Skip to main content
Erschienen in: BMC Cancer 1/2019

Open Access 01.12.2019 | Research article

Comparing cancer incidence, stage at diagnosis and outcomes of First Nations and all other Manitobans: a retrospective analysis

verfasst von: Tara C. Horrill, Lindsey Dahl, Esther Sanderson, Garry Munro, Cindy Garson, Carole Taylor, Randy Fransoo, Genevieve Thompson, Catherine Cook, Janice Linton, Annette S. H. Schultz

Erschienen in: BMC Cancer | Ausgabe 1/2019

Abstract

Background

Globally, epidemiological evidence suggests cancer incidence and outcomes among Indigenous peoples are a growing concern. Although historically cancer among First Nations (FN) peoples in Canada was relatively unknown, recent epidemiological evidence reveals a widening of cancer related disparities. However evidence at the population level is limited. The aim of this study was to explore cancer incidence, stage at diagnosis, and outcomes among status FN peoples in comparison with all other Manitobans (AOM).

Methods

All cancers diagnosed between April 1, 2004 and March 31, 2011 were linked with the Indian Registry System and five provincial healthcare databases to compare differences in characteristics, cancer incidence, and stage at diagnosis and mortality of the FN and AOM cohorts. Cox proportional hazard regression models were used to examine mortality.

Results

The FN cohort was significantly younger, with higher comorbidities than AOM. A higher proportion of FN people were diagnosed with cancer at stages III (18.7% vs. 15.4%) and IV (22.4% vs. 19.9%). Cancer incidence was significantly lower in the FN cohort, however, there were no significant differences between the two cohorts after adjusting for age, sex, income and area of residence. No significant trends in cancer incidence were identified in either cohort over time. Mortality was generally higher in the FN cohort.

Conclusions

Despite similar cancer incidence, FN peoples in Manitoba experience poorer survival. The underlying causes of these disparities are not yet understood, particularly in relation to the impact of colonization and other determinants of health.
Hinweise

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Abkürzungen
AOM
All other Manitobans
FN
First Nations
ICD
International Classification of Diseases
MCHP
Manitoba Center for Health Policy
RHA
Regional health authority

Comparing cancer incidence, stage at diagnosis and outcomes of first nations and all other Manitobans: a retrospective analysis

Globally, epidemiologic reporting of cancer incidence and outcomes among Indigenous peoples is a growing concern [1]. Historically, cancer among First Nations (FN) peoples in Canada was relatively unknown [2]; however, recent epidemiological evidence reveals increasing cancer incidence among FN peoples [3]. In addition, this evidence demonstrates that FN people are diagnosed at later stages of cancer, and their survival is poorer. While the emerging epidemiologic evidence is telling a story of growing concern, there remains significant gaps in data due to limitations in monitoring trends and reporting patterns [4].

Background

In Canada, previous studies show an increase in cancer incidence in FN people compared to non-FN people, however this observed trend seems to be cancer site specific [510]. Cancer stage at diagnosis is an important prognostic indicator, and evidence suggests FN people are more likely to be diagnosed at later stages than non-FN Canadians [1113]. Disparities in survival are equally concerning. Cancer mortality is higher among FN in Ontario than non-FN people [7], and while trends indicate the mortality for breast and colorectal cancers are decreasing among non-FN, they are increasing among FN people. Colorectal cancer mortality in particular increased 8-fold among FN people in Manitoba between 1984 and 2008 [11]. FN people experience significantly poorer cancer survival than non-FN in multiple Canadian provinces [57, 12, 1416], independent of stage at diagnosis [14], income, or rural residency [16].
Similar disparities in cancer incidence and outcomes between Indigenous peoples and their non-Indigenous counterparts are reported elsewhere. In the United States, cancer mortality rates have progressively declined among non-Indigenous Americans, yet remain unchanged among Indigenous peoples [1719]. Indigenous peoples in Australia are more likely to have advanced disease at diagnosis and less likely to receive certain cancer treatments [8, 2022]. Similarly, Indigenous peoples in New Zealand (Maori) experience significantly higher incidence of cancer than non-Indigenous New Zealanders, with evidence of disparities in stage at diagnosis, treatments received, and survival [8, 2325].
Emerging evidence demonstrates the shifting trends that are causing the widening disparity between FN people and the general population, yet epidemiological studies focused on cancer incidence and stage at diagnosis at the population level are sparse, particularly within the Canadian context. Within Manitoba, breast, colorectal and cervical cancers have been studied in the FN population, however, to date, no study has investigated general cancer trends. In this article, findings from a secondary analysis of provincial health administrative data are reported and address three objectives: a) to describe the demographics, comorbidities, site and stage of cancer at diagnosis among FN people and All Other Manitobans (AOM) who received a cancer diagnosis between April 1, 2004 and March 31, 2011; b) to compare annual crude and adjusted incidence rates for each cohort; c) to investigate mortality outcomes for each cohort. Supporting this research to address identified research gaps is an interdisciplinary team of researchers and FN community members.

Methods

Study context

In Canada, the term ‘Indigenous peoples’ is used to describe three distinct groups: First Nations (FN), Metis and Inuit. Among FN people, those registered with the federal government are referred to as “status First Nations” or “registered Indians”. As of 2016, Indigenous peoples represent approximately 4.9% of the Canadian population (36 million); of those, approximately 58.4% self-reported as FN [26]. Within Manitoba, Indigenous peoples represent approximately 18% of the population, of which 58.4% self-reported as FN, with nearly all (97.5%) identifying as status FN [27].
Healthcare services in Canada are publicly funded, providing universal coverage for all medically necessary hospital, physician, and specialist services. While often referred to as the “Canadian healthcare system”, delivery of healthcare services, including cancer control, is the responsibility of each provincial or territorial government, in essence creating a network of 13 healthcare systems. For status FN people living on reserve lands, healthcare services are delivered or funded by the federal government (public health, prevention and limited primary care), but hospital and physician services are provided by the provincial/territorial government regardless of status. Thus, provincial health administrative data contain information for all patients with a cancer diagnosis in Manitoba (FN and AOM).

Study design and data sources

A population-based secondary analysis of administrative health services data of newly diagnosed adult cancer patients (≥ 18 years of age) within the province of Manitoba between April 1, 2004 and March 31, 2011 was conducted. Patients with a diagnosis of “non-melanoma skin & in situ skin” cancers were excluded. Multiple datasets housed in the Manitoba Population Research Data Repository (Repository) at the Manitoba Centre for Health Policy (MCHP) were linked in order to compare differences in socio-demographic and clinical characteristics, incidence trends over time, and health outcomes between status-FN and AOM. Data files in the repository do not contain names or other identifying information; an encrypted identifier allows linkage across files, while protecting privacy. The specific data files used in this study included:
1.
The Manitoba Health Insurance Registry, which contains person-level demographic information and residential postal codes for nearly all Manitobans, including FN people;
 
2.
Hospital Abstracts, which includes International Classification of Diseases (ICD-10-CA) diagnostic codes and Canadian Classification for Health Interventions (CCI) procedure codes for all hospital admissions in Manitoba;
 
3.
Medical Services, which contains information on physician and nurse practitioner services provided in Manitoba (and the associated ICD-9-CM);
 
4.
The Vital Statistics Mortality Registry, which contains records of each person who has died in Manitoba and the primary cause of death;
 
5.
The Manitoba Cancer Registry (MCR), which contains records on all incident cases of diagnosed cancer, including cancer treatment, tumor characteristics, and cancer site and stage at diagnosis;
 
6.
The Census of Canada aggregate data file, which contains information used to create quintiles of area-level income, a commonly used indicator of socioeconomic status; and
 
7.
The Indian Registry System (IRS), a national database maintained by the Department of Indigenous Services Canada, lists all registered FN people to determine eligibility for benefits provided by the federal government. Identification of FN patients within administrative data requires linkage of the IRS with encrypted personal health numbers.
 
Approval for this study was obtained from the University of Manitoba Education & Nursing Research Ethics Board, the Manitoba Health Information Privacy Committee, CancerCare Manitoba, and the Health Information Research Governance Committee at Nanaandawewigamig (First Nations Health and Social Secretariat of Manitoba).

Defining variables and statistical analyses for each objective

Objective 1: Cancer patient characteristics

Descriptive characteristics of FN and AOM patients with a diagnosis of cancer between 2004 and 2011 were measured at the time of diagnosis, and included: age, sex, area of residence, area-level income, and Charlson Comorbidity Index score. Residence was measured at the Regional Health Authority (RHA) level. Five RHAs in Manitoba are responsible for delivering health services within their designated geographic area, and the RHA corresponding to the patients’ postal code was used to indicate residence. Income quintiles, a predictor of health and health service use [26, 27], were calculated separately for urban (Winnipeg and Brandon) and rural (all other areas of Manitoba) areas based on the average household incomes for each Census dissemination area. Each patient was assigned the income quintile of the dissemination area that contained their postal code. The Charlson Comorbidity Index provided a valid measure of each patient’s health status at the time of first cancer diagnosis [28]. Comorbidities were identified using ICD-10-CA codes from the hospital discharge abstract and ICD-9-CM codes from the medical claims database during the one-year period prior to cancer diagnosis. Cancer stage is contained in the MCR according to the American Joint Committee on Cancer Staging system [29]. This system is used to stage the severity of cancer between stages I (least severe) and IV (most severe) based on the pathological and clinical characteristics of the cancer. A fifth ‘unknown’ category was used for cancers that could not be assessed. Finally, the site of cancer according to the International Classification of Diseases for Oncology Third Edition (ICD-O3) is also recorded in the MCR. Differences in these variables between FN and AOM cohorts were tested for significance using t-tests for continuous variables, and chi-squared tests for categorical variables.

Objective 2: Cancer incidence

Annual crude and adjusted rates of cancer incidence were calculated in the FN and AOM populations for each year within the study time period. For each annual rate, a count of all cancers diagnosed from the sixteen ICD-O3 site categories considered for this study were used as the numerators and the annual FN and AOM population counts of adults aged 18 years of age or older were used as the denominators. A generalized linear model with a negative binomial log link function was used to calculate adjusted annual incidence rates, controlling for age, sex, income quintile and area of residence recorded at the Regional Health Authority (RHA) level. Differences in incidence rates between FN and AOM populations were tested for significance using a chi-squared test and the trends over time were analyzed with linear regression models fit to the annual rates.

Objective 3: mortality

All-cause mortality and cancer-specific mortality were calculated for FN and AOM populations. Patients were followed for five years from the date of cancer diagnosis. Mortality information, including the date and primary cause of death, were identified using the Vital Statistics data file. Unadjusted and adjusted Cox proportional hazard regression models were used to examine the association between FN status and five year all-cause and cancer-specific mortality. Patient event times were calculated from the date of cancer diagnosis to the date of death, or were censored at five years if no evidence of death, or on the date of health insurance coverage discontinuation, which often indicates that the person has moved out of Manitoba. To examine the association between FN status and overall mortality, patient data was censored at the time of death for all non-cancer-related causes of death. When assessing cancer-specific mortality, a patient may die due to causes unrelated to the disease, therefore it was necessary to account for these competing risk events. Each adjusted model controlled for age, sex, RHA of residence, area-level income, Charlson comorbidity index, and the stage of cancer at time of diagnosis. All effect estimates are reported as hazard ratios with 95% confidence intervals and the significance level was p < 0.05. Analysis for each objective was done on the secure server at MCHP, using SAS statistical analysis software, V.9.4 (SAS Institute).

Results

Characteristics of patients with a first diagnosis of Cancer

In total, 38,076 adult Manitobans were diagnosed with a first cancer between 2004 and 2011, of which 1524 (4%) were FN people. FN people diagnosed with cancer were significantly younger than AOM (mean age 59.4 vs. 67.4 years; p < 0.0001). FN people diagnosed with cancer experienced significantly more co-morbidities as indicated by the Charlson Co-morbidity Index scores (1.4 vs. 1.0; p < 0.0001). There were higher proportions of FN people with a first time cancer diagnosis living in the lowest urban and rural income quintiles compared to AOM, with a decrease in proportion seen with increasing income. Among the AOM cohort, the proportions of patients within the urban and rural income quintiles were more evenly distributed (Table 1).
Table 1
Characteristics of Cancer Patients by FN Status and AOM
Characteristic
First Nations
n = 1524 (4%)
AOM
n = 36,552 (96%)
p value
Age (years) mean ± SD
59.4 ± 14.4
67.4 ± 14.1
< 0.0001
Female Sex
845 (55.4%)
18,386 (50.3%)
< 0.0001
Regional Health Authority
  
< 0.0001
 Interlake-Eastern
338 (22.2%)
3838 (10.5%)
 
 Northern
535 (35.1%)
724 (2.0%)
 
 Southern Health
88 (5.8%)
4213 (11.5%)
 
 Prairie Mountain Health
168 (11.0%)
5873 (16.1%)
 
 Winnipeg
382 (25.1%)
21,728 (59.4%)
 
 Public Trustee
13 (0.9%)
176 (0.5%)
 
Average household income quintiles
< 0.0001
 Rural 1 (lowest rural)
587 (38.5%)
1876 (5.1%)
 
 Rural 2
252 (16.5%)
2957 (8.1%)
 
 Rural 3
86 (5.6%)
3009 (8.2%)
 
 Rural 4
126 (8.3%)
2755 (7.5%)
 
 Rural 5 (highest urban)
61 (4.0%)
2364 (6.5%)
 
 Urban 1 (lowest urban)
219 (14.4%)
4963 (13.6%)
 
 Urban 2
79 (5.2%)
4896 (13.4%)
 
 Urban 3
42 (2.8%)
4815 (13.2%)
 
 Urban 4
36 (2.4%)
4310 (11.8%)
 
 Urban 5 (highest urban)
15 (1.0%)
4103 (11.2%)
 
Charlson Comorbidity Index Score, mean ± SD
1.4 ± 1.3
1.0 ± 1.1
< 0.0001
 Myocardial infarction
46 (3%)
704 (1.9%)
 
 Congestive heart failure
106 (7.0%)
2200 (6.0%)
 
 Peripheral vascular disease
53 (3.5%)
1175 (3.2%)
 
 Cerebrovascular disease
62 (4.1%)
1469 (4.0%)
 
 Dementia
21 (1.4%)
1146 (3.1%)
 
 Chronic pulmonary disease
263 (17.3%)
5544 (15.2%)
 
 Connective tissue disease
56 (3.7%)
726 (2.0%)
 
 Peptic ulcer disease
73 (4.8%)
602 (1.6%)
 
 Mild liver disease
66 (4.3%)
678 (1.9%)
 
 Diabetes without complications
514 (33.7%)
5286 (14.5%)
 
 Diabetes with complications
105 (6.9%)
656 (1.8%)
 
 Paraplegia and hemiplegia
14 (0.9%)
214 (0.6%)
 
 Renal disease
83 (5.4%)
962 (2.6%)
 
 Cancer
519 (34.1%)
13,515 (37.0%)
 
 Moderate or severe liver disease
14 (0.9%)
153 (0.4%)
 
 Metastatic carcinoma
71 (4.7%)
1059 (2.9%)
 
 HIV/AIDS
8 (0.5%)
20 (0.1%)
 

Cancer diagnoses by stage & site

Statistically significant differences in cancer stage at diagnosis were seen between the FN and AOM cohorts, with a higher proportion of FN patients diagnosed at stages III and IV (Table 2). Cancer site analysis also demonstrated statistically significant differences between FN patients and AOM. Notably, a significantly higher proportion of FN patients were diagnosed with cervical cancer, kidney cancer, and colorectal cancer (Table 3). A significantly lower proportion of FN patients were diagnosed with prostate cancer, melanoma, chronic lymphocytic leukemia, and bladder cancer. Given small numbers of some cancers, we are not able to report incidence of cancers by site and sex.
Table 2
Cancer Stage at Diagnosis by FN Status and AOM
Cancer Stage
First Nation (n = 1524)
AOM (n = 36,552)
p Value
I
362 (23.8%)
9217 (25.2%)
0.1972
II
340 (22.3%)
8763 (24.0%)
0.1356
III
285 (18.7%)
5637 (15.4%)
0.0005
IV
342 (22.4%)
7277 (19.9%)
0.0155
Unknown
195 (12.8%)
5658 (15.5%)
0.0044
Table 3
Cancer Site by FN Status
Cancer Site
FN (n = 1524)
AOM (n = 36,552)
p value
Bladder
13 (0.9%)
814 (2.2%)
0.0003
Breast
210 (13.8%)
5219 (14.3%)
0.5853
Cervix
43 (3.0%)
286 (0.8%)
< 0.0001
Chronic Lymphocytic Leukemia
7 (0.5%)
351 (1.8%)
0.0001
Colorectal
240 (15.7%)
5063 (13.9%)
0.0362
Kidney
136 (8.9%)
1177 (3.2%)
< 0.0001
Lung & Bronchus
205 (13.5%)
5306 (14.5%)
0.247
Melanoma
8 (0.5%)
988 (2.7%)
< 0.0001
Non-Hodgkin Lymphoma
65 (4.6%)
1609 (4.4%)
0.7985
Ovarian
32 (2.1%)
545 (1.5%)
0.0567
Pancreas
32 (2.1%)
914 (2.5%)
0.3247
Prostate
134 (8.8%)
4558 (12.5%)
< 0.0001
Stomach
29 (1.9%)
727 (2.0%)
0.8135
Thyroid
20 (1.3%)
667 (1.8%)
0.1409
Uterine
38 (2.5%)
1263 (3.5%)
0.0428
Other
355 (23.3%)
7051 (19.3%)
0.0714
The overall crude cancer incidence rate between 2004 and 2011 was significantly lower in the FN population (334.90 vs. 651.57 per 100,000; p < 0.0001), and annual crude cancer incidence rates were lower in the FN population for each year within the study period (Table 4). However, after adjusting for age, sex (Table 5), and further adjusting for income and area of residence (Table 6), there were no differences in the annual incidence rates, except for the year 2008/09 in which FN patients had a higher incidence once adjusted for both age and sex, and income and area of residence (331.9 vs. 278.6 per 100,000; p = 0.0171) (Table 6). There were no significant trends over time in either cohort.
Table 4
Crude Rates of Cancer Incidence (total) per 100,000 by FN Status
Fiscal
Year
First Nation
AOM
p value
Count
IR per 100,000
95%
CI
Count
IR per
100,000
95%
CI
2004/2005
191
306.04
264.09–350.96
5383
653.55
635.96–670.88
< 0.0001
2005/2006
194
303.15
264.81–350.63
5226
631.49
614.84–649.10
< 0.0001
2006/2007
202
307.90
268.24–353.43
5393
648.05
630.99–665.58
< 0.0001
2007/2008
209
310.90
271.48–356.04
5473
649.37
632.62–667.04
< 0.0001
2008/2009
273
395.75
351.48–445.59
5679
666.46
649.23–683.90
< 0.0001
2009/2010
256
359.43
317.99–406.27
5691
657.56
640.59–674.75
< 0.0001
2010/2011
259
352.24
311.85–397.86
5749
653.76
637.19–670.94
< 0.0001
Overall
1584
334.90
318.81–351.81
38,594
651.57
645.11–658.11
< 0.0001
Table 5
Annual incidence rates (adjusted for age and sex)
Fiscal
Year
First Nation
AOM
p-value
Count
IR per
100,000
95% CI
Count
IR per
100,000
95% CI
2004/2005
191
265.68
212.00–332.94
5383
259.21
218.07–308.11
0.864
2005/2006
194
262.48
209.67–328.60
5226
259.54
218.31–308.57
0.938
2006/2007
202
263.65
210.93–329.55
5393
268.04
225.47–318.65
0.908
2007/2008
209
254.06
203.46–317.25
5473
265.58
223.44–315.67
0.756
2008/2009
273
332.64
261.32–398.34
5679
268.58
226.00–319.19
0.184
2009/2010
256
290.99
234.95–360.40
5691
265.23
223.14–315.26
0.505
2010/2011
259
283.98
229.42–351.51
5749
262.61
220.97–312.10
0.574
Overall
1584
272.21
228.18–324.73
38,594
265.20
224.40–313.43
0.832
Table 6
Annual incidence rates (adjusted for age, sex, income and area of residence)
Fiscal
Year
First Nation
AOM
p-value
Count
IR per
100,000
95% CI
Count
IR per
100,000
95% CI
2004/2005
191
263.76
224.37–306.40
5383
281.01
265.35–296.73
0.449
2005/2006
194
261.44
225.45–306.74
5226
267.29
253.31–283.38
0.790
2006/2007
202
260.62
223.92–303.33
5393
276.97
261.36–292.26
0.457
2007/2008
209
259.80
223.70–301.73
5473
270.22
256.07–286.23
0.626
2008/2009
273
331.88
290.18–379.57
5679
278.60
263.34–294.27
0.017
2009/2010
256
301.92
263.45–346.00
5691
274.63
259.96–290.14
0.201
2010/2011
259
295.81
255.66–335.36
5749
273.99
259.37–289.49
0.369
Overall
1584
274.51
255.01–295.50
38,594
274.27
262.71–286.34
0.983

Cancer mortality

The FN cohort had a significantly higher risk of all-cause mortality than the AOM cohort, both before (HR 1.12 95% CI 1.045–1.196) and after adjustment (HR 1.26, 95% CI 1.178–1.351), and significantly higher risk of all cause-mortality 5 years post cancer diagnosis (HR 1.23, 95% CI 1.152–1.321) (Table 7). The FN cohort also had a higher risk of overall cancer-specific mortality in both the crude (HR 1.126, 95% CI 1.046–1.211), and adjusted models (HR 1.108, 95% CI 1.009–1.218), and in 5-year cancer-specific mortality (HR 1.099, 95% CI 1.001–1.207).
Table 7
Mortality Hazard Ratiosa
 
HR
95% CI
P-value
Crude All-Cause Mortality
1.119
1.045–1.196
0.0011
Adjusted All-Cause Mortality
1.262
1.178–1.351
< 0.0001
Adjusted All-Cause Mortality 5 Years Post-Diagnosis
1.234
1.152–1.321
< 0.0001
Crude Cancer-Specific Mortality
1.126
1.046–1.211
0.0015
Adjusted Cancer-Specific Mortality
1.108
1.009–1.218
0.0322
Adjusted Cancer-Specific Mortality 5 Years Post-Diagnosis
1.099
1.001–1.207
0.0487
aAdjusted models have controlled for age, sex, area of residence by RHA, area-level income, Charlson comorbidity index, and stage of cancer at time of diagnosis

Discussion

This study aimed to describe the characteristics of FN patients and AOM diagnosed with cancer between 2004 and 2011, and examine cancer incidence, site, stage at diagnosis, and mortality. Our results indicate that the FN cohort was significantly younger, and had a significantly higher Charlson Comorbidity Index compared to the AOM cohort. Although crude incidence rates among the FN cohort were half that of AOM, these differences were not sustained after adjusting for age, sex, income and area of residence. We found no significant trends in cancer incidence in either cohort over time. We did, however, find significant differences in cancer sites diagnosed between cohorts. Notably, our results show a higher proportion of FN patients diagnosed with cancer at stages III and IV than AOM, and a higher risk of all-cause mortality and cancer-specific mortality in the FN cohort.
We found that the proportion of prostate, bladder, and uterine cancers were significantly lower in the FN cohort, while the proportion of cervical, colorectal and kidney cancers were significantly higher in the FN cohort compared to AOM. Elsewhere in Canada, incidence of bladder, breast and uterine cancers and melanoma were lower among FN people in Ontario [7], and lower incidence of breast and prostate cancers were found among FN people in British Columbia [6]. A significantly higher incidence of colorectal and cervical cancers have been found among FN people in British Columbia and Manitoba [6, 9, 11], and a significantly higher incidence of colorectal, kidney and cervical cancers among FN people in Ontario [5, 7]. Differences in cancer incidence may be related to genetic risk or environmental exposures, however, we wish to draw attention to alternative factors that may explain, in part, some of these differences. Higher proportions of cervical cancer among FN women may suggest poor access to screening services, which identify pre-cancerous changes that can be treated to prevent cancer. A recent meta-analysis found increased risk of invasive cervical cancer and cervical cancer-related mortality among Indigenous women compared to non-Indigenous women, yet no increased risk of cervical dysplasia or carcinoma in situ (precursors to cervical cancer) [30]. These results suggest “structural, social, or individual barriers to screening, rather than baseline risk factors, are influencing poor health outcomes” [30, p148].
Poor access to cervical cancer screening may be related to geographical availability of services as well as access to culturally safe services, which are particularly important within the context of historical trauma and experiences of residential school survivors, and the invasive nature of cervical cancer screening [3134]. Within Canada, research indicates Indigenous women face multiple structural barriers to accessing cervical cancer screening (including historical, political, socioeconomic, and health systems factors), many of are rooted in colonial history [32, 33]. Within Manitoba, FN women over 40 are less likely to receive a pap test than AOM, FN women younger than 25 are more likely to receive a pap test, and there is no difference between FN and AOM in pap testing for women 25–39 [9]. Higher incidence of cervical cancer among FN women may also indicate poor access to follow-up care after an abnormal Pap test result [6, 33].
In our study, a higher proportion of FN people compared with AOM were diagnosed with cancer at stages III (18.7% vs. 15.4%) and IV (22.4% vs. 19.9%). Several other Canadian studies have demonstrated similar patterns of late-stage diagnosis, with FN women more likely to be diagnosed with breast cancer at later stages than non-FN women [1113]. This is particularly concerning given that cancer stage at diagnosis has a significant impact on treatment options and cancer outcomes, and is an important indicator of the quality of, and access to screening and early detection services [35, 36]. FN people in Canada experience difficulty accessing primary care [37, 38] and diagnostic services [39, 40], which may be contributing to higher rates of stage III and IV diagnoses. Many FN communities are located in rural or remote areas characterized by low population density, poor transportation infrastructure, limited resources for diagnostics and high turnover of healthcare professionals. This results in limited or non-existent access to local healthcare services, poor continuity of care, and compromised quality of care [34, 4044]. As such, many FN patients must travel to access basic diagnostic services, treatment and supportive care. Lengthy travel time, coupled with transportation that is not feasible, convenient or affordable creates significant barriers to accessing cancer care [4547]. Although there are resources to support medical travel, particularly for status FN people, accessing these resources can come with challenges [39, 42].
Accessing health care, however, requires more than service or healthcare provider availability – patients must also feel that their concerns are heard, and that care will be provided that is free of judgment and culturally safe [48]. Cultural safety is an approach to delivering care that is based on establishing trusting and reciprocal relationships between a patient and their healthcare provider [49]. Lack of culturally safe care has been noted to be a barrier to accessing cancer care among FN people [34, 45, 50, 51]. Racism, discrimination, and fear of judgment have been noted to impede access to both primary care [37, 38] and cancer care [32, 47, 50, 52, 53], by causing patients to delay or avoid accessing care. These experiences are further exacerbated by histories of historical trauma, residential school attendance and Indian hospitals, which have been noted to increase distrust of healthcare providers. Feelings of distrust, negative experiences within institutional settings, culturally incongruous systems and experiences with marginalization and racism can result in patients delaying or avoiding seeking care [42, 46, 47, 53]. It is unclear to what extent healthcare providers are aware of the impact of their actions on FN peoples access to healthcare, and more research is needed to understand this relationship.
Finally, our results show that FN people had a higher risk of all-cause mortality and cancer-specific mortality than AOM both before and after adjustment for age, sex, cancer stage at diagnosis, income, region of residence and comorbidities. Our results also show that FN patients had a higher risk of death from any cause (HR 1.234, 95% CI 1.15–1.32, p < 0.0001) and a higher risk of cancer-related death (HR 1.099, 95% CI 1.001–1.207) at 5 years post-cancer diagnosis than AOM. These results are similar to other studies in Canada, indicating higher cancer-related mortality among FN people [6, 7, 1416].
While disparities in cancer-related survival are multifactorial, the main determinant of survival is cancer stage at diagnosis [29]. Underlying these disparities, however, are a host of health inequities experienced by FN people in Canada, some of which are discussed above. Health inequities are the systematic and unjust differences in health between socioeconomic groups; these differences are generated by social, economic and environmental factors and contexts amenable to change, and are not a result of ‘lifestyle’ or personal choices [54]. Within Canada, a significant body of evidence demonstrates the substantial health inequities experienced by Indigenous peoples (including FN people) [55, 56]. Researchers, healthcare providers and policy makers must consider the context of these inequities, and how they are, at least in part, “the direct and indirect present-day symptoms of a history of loss of lands and autonomy and the results of the political, cultural, economic and social disenfranchisement that ensued” ([57], p59). Although individual characteristics, comorbidities, tumor biology, cancer treatment impact, and access to/use of healthcare services impact survival [6, 15, 58], an agenda to improve cancer outcomes among Indigenous peoples, including FN people, must also acknowledge and address health and social inequities. In particular, the tendency to focus on ‘lifestyle’ or behavioral risk factors (i.e., smoking, diet, alcohol) and education about risk factors, while ignoring the “drivers of these behaviors” must be disrupted ([59], pS517]). Our intent here is to draw attention to the ‘causes of the causes’ and determinants of Indigenous health, rather than perpetuate the discourse that focuses solely on genetic and ‘lifestyle’ risk factors as potential causes of the disparities and inequities described.

Limitations

There are several limitations to this study. First, only those individuals registered under the Indian Act were included in the FN cohort, with non-registered FN people subsequently included with AOM. This may have resulted in an underrepresentation of the differences in stage at cancer diagnosis and outcomes given that non-registered FN people experience many of the same socioeconomic conditions, access to healthcare issues, and colonial history as registered FN people. At present, there is no mechanism to identify non-registered FN people in these datasets. Second, we were not able to analyze differences in mortality between the FN and AOM cohorts by disease site, and there may be significant differences in mortality and survival depending on cancer site. Further investigation is needed.

Conclusion

Our study found no significant differences in overall adjusted cancer incidence between FN people and AOM, and no significant trends over time in overall cancer incidence in either cohort. However, a significantly higher proportion of FN people were diagnosed with cancer at stages III and IV compared to AOM. FN people also experienced higher all-cause mortality and cancer-specific mortality. No significant differences were seen between cohorts in 5-year site-specific mortality. The underlying causes of these disparities are complex, and not yet well understood, particularly in relation to the impact of colonization and other structural determinants of health. Further research is needed to better understand the complex and interactive nature of factors resulting in later cancer diagnoses among FN people.

Acknowledgments

The authors acknowledge the Manitoba Centre for Health Policy for use of data obtained in the Manitoba Population Research Data Repository (HIPC #2017/2018-34). The results and conclusions are those of the authors and no official endorsement by the Manitoba Centre for Health Policy, Manitoba Health, or other data providers is intended or should be inferred. Data used in this study are from the Manitoba Population Research Data Repository housed at the Manitoba Centre for Health Policy, University of Manitoba, and were derived from data provided by Manitoba Health, Vital Statistics, Statistics Canada and CancerCare Manitoba.
This research was approved by the University of Manitoba Education & Nursing Research Ethics Board (E2017:043), the Manitoba Health Information Privacy Committee, CancerCare Manitoba, and the Health Information Research Governance Committee. The Education & Nursing Research Ethics Board waived the need to obtain consent for the analysis and publication of the retrospectively obtained and anonymized data for this study.
Not applicable.

Competing interests

The authors declare that they have no competing interests.
Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://​creativecommons.​org/​licenses/​by/​4.​0/​), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://​creativecommons.​org/​publicdomain/​zero/​1.​0/​) applies to the data made available in this article, unless otherwise stated.

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Literatur
2.
Zurück zum Zitat Waldram JB, Herring DA, Young TK. Aboriginal health in Canada: historical, cultural, and epidemiological perspectives. 2nd ed. Toronto: University of Toronto Press; 2006. Waldram JB, Herring DA, Young TK. Aboriginal health in Canada: historical, cultural, and epidemiological perspectives. 2nd ed. Toronto: University of Toronto Press; 2006.
8.
Zurück zum Zitat Moore SP, Antoni S, Colquhoun A, et al. Cancer incidence in indigenous people in Australia, New Zealand, Canada, and the USA: a comparative population-based study. Lancet Oncol. 2015;16:1483–92.PubMedCrossRef Moore SP, Antoni S, Colquhoun A, et al. Cancer incidence in indigenous people in Australia, New Zealand, Canada, and the USA: a comparative population-based study. Lancet Oncol. 2015;16:1483–92.PubMedCrossRef
10.
Zurück zum Zitat Young TK, Kliewer E, Blanchard J, Mayer T. Monitoring disease burden and preventative behavior with data linkage: cervical cancer among aboriginal people in Manitoba, Canada. Am J Public Health. 2000;90:1466–8.PubMedPubMedCentralCrossRef Young TK, Kliewer E, Blanchard J, Mayer T. Monitoring disease burden and preventative behavior with data linkage: cervical cancer among aboriginal people in Manitoba, Canada. Am J Public Health. 2000;90:1466–8.PubMedPubMedCentralCrossRef
12.
Zurück zum Zitat Alvi RA. Breast, cervical and colorectal cancer survival rates for northern Saskatchewan residents and first nations. Dissertation, University of Saskatchewan; 1999. Alvi RA. Breast, cervical and colorectal cancer survival rates for northern Saskatchewan residents and first nations. Dissertation, University of Saskatchewan; 1999.
13.
Zurück zum Zitat Sheppard AJ, Chiarelli AM, Marrett LD, Mirea L, Nishri DE, Trudeau ME. Detection of later stage breast cancer in first nations women in Ontario, Canada. Can J Public Heal. 2010;101:101–5.CrossRef Sheppard AJ, Chiarelli AM, Marrett LD, Mirea L, Nishri DE, Trudeau ME. Detection of later stage breast cancer in first nations women in Ontario, Canada. Can J Public Heal. 2010;101:101–5.CrossRef
20.
Zurück zum Zitat Cunningham J, Rumbold AR, Zhang X, Condon JR. Incidence, aetiology, and outcomes of cancer in indigenous peoples in Australia. Lancet Oncol. 2008;9:585–95.PubMedCrossRef Cunningham J, Rumbold AR, Zhang X, Condon JR. Incidence, aetiology, and outcomes of cancer in indigenous peoples in Australia. Lancet Oncol. 2008;9:585–95.PubMedCrossRef
23.
Zurück zum Zitat Jeffreys M, Stevanovic V, Tobias M, Lewis C, Ellison-Loschmann L, Pearce N, Blakely T. Ethnic inequalities in cancer survival in New Zealand: linkage study. Am J Pub Health. 2005;95:834–7.CrossRef Jeffreys M, Stevanovic V, Tobias M, Lewis C, Ellison-Loschmann L, Pearce N, Blakely T. Ethnic inequalities in cancer survival in New Zealand: linkage study. Am J Pub Health. 2005;95:834–7.CrossRef
24.
Zurück zum Zitat Obertova Z, Scott N, Brown C, Stewart A, Lawrenson R. Survival disparities between Maori and non-Maori men with prostate cancer in New Zealand. BJU Int. 2015;115:24–30.PubMedCrossRef Obertova Z, Scott N, Brown C, Stewart A, Lawrenson R. Survival disparities between Maori and non-Maori men with prostate cancer in New Zealand. BJU Int. 2015;115:24–30.PubMedCrossRef
25.
Zurück zum Zitat Obertova Z, Lawrenson R, Scott N, et al. Treatment modalities for Maori and New Zealand European men with localised prostate cancer. Int J Clin Oncol. 2015;20:814–20.PubMedCrossRef Obertova Z, Lawrenson R, Scott N, et al. Treatment modalities for Maori and New Zealand European men with localised prostate cancer. Int J Clin Oncol. 2015;20:814–20.PubMedCrossRef
26.
Zurück zum Zitat Statistics Canada (2017) Canada [Country] and Canada [Country] (Table): Census Profile. Statistics Canada Catalogue No. 98–316-X2016001. Statistics Canada (2017) Canada [Country] and Canada [Country] (Table): Census Profile. Statistics Canada Catalogue No. 98–316-X2016001.
27.
Zurück zum Zitat Statistics Canada (2017) Manitoba [Province] and Canada [Country] (Table): Census Profile. Statistics Canada Catalogue No. 98–316-X2016001. Statistics Canada (2017) Manitoba [Province] and Canada [Country] (Table): Census Profile. Statistics Canada Catalogue No. 98–316-X2016001.
28.
Zurück zum Zitat Deyo RA, Cherkin DC, Ciol MA. Adapting a clinical comorbidity index for use with ICD-9-CM administrative databases. J Clin Epidemiol. 1992;45:613–9.PubMedCrossRef Deyo RA, Cherkin DC, Ciol MA. Adapting a clinical comorbidity index for use with ICD-9-CM administrative databases. J Clin Epidemiol. 1992;45:613–9.PubMedCrossRef
29.
Zurück zum Zitat Edge SB, American Joint Committee on Cancer. AJCC Cancer staging manual. 7th ed. New York: Springer; 2010.CrossRef Edge SB, American Joint Committee on Cancer. AJCC Cancer staging manual. 7th ed. New York: Springer; 2010.CrossRef
30.
Zurück zum Zitat Vasilevska M, Ross SA, Gesink D, Fisman DN. Relative risk of cervical cancer in indigenous women in Australia, Canada, New Zealand, and the United States: a systematic review and meta-analysis. J Pub Hlth Pol. 2012;33:148–64 https://doi.org/10.1057/jphp.2012.8. Vasilevska M, Ross SA, Gesink D, Fisman DN. Relative risk of cervical cancer in indigenous women in Australia, Canada, New Zealand, and the United States: a systematic review and meta-analysis. J Pub Hlth Pol. 2012;33:148–64 https://​doi.​org/​10.​1057/​jphp.​2012.​8.
32.
Zurück zum Zitat MacDonald C, Martin-Misener R, Steenbeek A, Browne A. Honouring stories: Mi’kmaq women’s experiences with pap screening in eastern Canada. Can J Nrs Res. 2015;47:72–96.CrossRef MacDonald C, Martin-Misener R, Steenbeek A, Browne A. Honouring stories: Mi’kmaq women’s experiences with pap screening in eastern Canada. Can J Nrs Res. 2015;47:72–96.CrossRef
34.
Zurück zum Zitat Black AT. Cervical cancer screening strategies for aboriginal women. Pimitisiwin. 2009;7:157–79. Black AT. Cervical cancer screening strategies for aboriginal women. Pimitisiwin. 2009;7:157–79.
41.
Zurück zum Zitat Hotson KE, Macdonald SM, Martin BD. Understanding death and dying in select first nations communities in northern Manitoba: issues of culture and remote service delivery in palliative care. Int J Circumpolar Health. 2004;63:25–38.PubMedCrossRef Hotson KE, Macdonald SM, Martin BD. Understanding death and dying in select first nations communities in northern Manitoba: issues of culture and remote service delivery in palliative care. Int J Circumpolar Health. 2004;63:25–38.PubMedCrossRef
44.
Zurück zum Zitat Minore B, Boone M, Katt M, Kinch P, Birch S, Mushquash C. The effects of nursing turnover on continuity of care in isolated first nation communities. Can J Nurs Res. 2005;37:86–100.PubMed Minore B, Boone M, Katt M, Kinch P, Birch S, Mushquash C. The effects of nursing turnover on continuity of care in isolated first nation communities. Can J Nurs Res. 2005;37:86–100.PubMed
47.
Zurück zum Zitat Rosicki A. Understanding barriers and facilitators to breast cancer screening among urban first nations women. Dissertation, Simon Fraser University; 2010. Rosicki A. Understanding barriers and facilitators to breast cancer screening among urban first nations women. Dissertation, Simon Fraser University; 2010.
53.
Zurück zum Zitat Jensen-Ross C. Cervical screening among southern Alberta first nations women living off-reserve. Dissertation, University of Lethbridge; 2006. Jensen-Ross C. Cervical screening among southern Alberta first nations women living off-reserve. Dissertation, University of Lethbridge; 2006.
56.
Zurück zum Zitat Smylie J, Firestone M. the health of indigenous peoples. In: Raphael D, editor. Social determinants of health: Canadian perspectives. 2nd ed. Toronto: Canadian Scholars’ Press; 2016. Smylie J, Firestone M. the health of indigenous peoples. In: Raphael D, editor. Social determinants of health: Canadian perspectives. 2nd ed. Toronto: Canadian Scholars’ Press; 2016.
57.
Zurück zum Zitat Adelson N. The embodiment of inequity. Can J Pub Health. 2005;96(S2):S45–61.CrossRef Adelson N. The embodiment of inequity. Can J Pub Health. 2005;96(S2):S45–61.CrossRef
58.
Metadaten
Titel
Comparing cancer incidence, stage at diagnosis and outcomes of First Nations and all other Manitobans: a retrospective analysis
verfasst von
Tara C. Horrill
Lindsey Dahl
Esther Sanderson
Garry Munro
Cindy Garson
Carole Taylor
Randy Fransoo
Genevieve Thompson
Catherine Cook
Janice Linton
Annette S. H. Schultz
Publikationsdatum
01.12.2019
Verlag
BioMed Central
Erschienen in
BMC Cancer / Ausgabe 1/2019
Elektronische ISSN: 1471-2407
DOI
https://doi.org/10.1186/s12885-019-6296-7

Weitere Artikel der Ausgabe 1/2019

BMC Cancer 1/2019 Zur Ausgabe

Update Onkologie

Bestellen Sie unseren Fach-Newsletter und bleiben Sie gut informiert.