Cancer incidence in eastern Morocco: cancer patterns and incidence trends, 2005–2012

According to WHO estimates, cancer causes more deaths than all cardiovascular diseases [1]. Therefore, cancer has become a major public health problem worldwide [2, 3]. The most common tumors worldwide were lung cancer with 1.8 million cases (13.0% of total), breast cancer with 1.7 million cases (11.9% of total) and the colorectal cancer with 1.4 million cases (9.7% of total). Similarly, cancers that cause the highest rate of deaths are cancers of the lung (1.6 million deaths, 19.4% of total), liver (0.8 million deaths, 9.1% of total) and stomach (0.7 million deaths, or 8.8% of total) [1]. In 2012, the overall cancer burden reached 14.1 million new cases compared to 12.7 million in 2008 [4, 5]. Similarly, 8.2 million deaths have been attributed to cancer during 2012 (13% of all deaths worldwide) compared to 7.6 million deaths in 2008 [4, 5].

In 2012, more than half of all cancer cases (56.8%) and deaths caused by cancer (64.9%) were recorded in the least developed regions of the world [1]. For example in Africa, there were 846,961 cases of cancer and 591,161 cancer deaths in 2012 [1]. Accordingly, epidemiologic studies predict 1.2 million new cancer cases in Africa with more than 970,000 deaths by 2030 if adequate control and prevention measures are not taken promptly [1, 6].

In Morocco, cancer is a major health problem and it is the second leading cause of mortality after cardiovascular diseases with 10.7% of all deaths [7]. However, there are only two population-based cancer registries in Morocco at the present time. The Casablanca registry was founded in March 2003 and the Rabat registry was created in January 2005. These registries have provided important information on cancer patterns in western Morocco [8‐12]. In Eastern Morocco, nothing is known about cancer incidence and therefore, in this study, we report for the first time the cancer incidence trends, the distribution and the socioeconomic profile of incident cancer cases in Eastern Morocco over a period of eight years between 2005 and 2012.

Cancer is one of the major health problems worldwide [1, 4, 5]. Hence, it is very important to conduct epidemiological studies to identify risk factors and to develop programs for cancer control and prevention. In Western countries, the risk of cancer increases with age, and therefore, individuals aged 65 and over have the highest incidence rates [23]. In addition, because of early diagnosis and more effective treatments, there have been notable improvements in survival for most cancers [23]. Unlike Western countries, cancer seems to affect a younger population in our study. The most affected age group by cancer was 45–54 years, which accounted for 27% of cases, and the mean age of patients diagnosed with cancer was 54.1 years. It is important to mention that childhood cancer (0–14 years) accounted for only 0.5% of all cancers, and were under-represented in this study because the Regional Oncology Center typically manages adult cancer patients. Therefore, the age of occurrence of cancer in Eastern Morocco may be even younger. This finding is consistent with our recently published report on caner prevalence in Eastern Morocco [14].

In our study, the mean age of patients diagnosed with cancer was higher in men than in women (58.1 years versus 52.1 years). This indicates that women are affected by cancer at a younger age than men (p < 0.001). Similar results were observed with the Moroccan populations of Casablanca, Rabat and Fez [8, 12, 24, 25].

As shown in Table 1, the sex ratio observed in our study is much higher than that reported in Casablanca, Rabat and Fez, as well as in other countries in North Africa, Asia, Europe and USA [8, 9, 12, 23, 25‐28]. Moreover, the crude incidence observed in 2012 was higher in females than males (80.3 per 100,000 women versus 42.6 per 100,000 men). Since the structure of the population of Eastern Morocco showed a sex ratio of female to male of 1.06 during the study period 2006–2012 [13], these data suggest that in Eastern Morocco, women are more affected by cancer than men, which is in agreement with our recently published report on caner prevalence in Eastern Morocco [14]. This great difference in incidence between men and women can be explained by differences in lifestyle, and/or the willingness to treat cancer between men and women.

Our retrospective analysis showed that for both sexes combined and for all cancer sites, breast cancer was the commonest followed by cervix uteri, colon-rectum, lung, nasopharynx, and stomach cancers. In males, lung cancer ranked first, followed respectively by colon-rectum, nasopharynx, prostate, and stomach cancers. Among the females, breast cancer was the most frequent, followed respectively by cervix uteri, colon-rectum, ovarian, and stomach cancer. These distribution patterns of cancers are quite different from those observed in Rabat and Casablanca registries [10, 11, 29]. For example, in females, the thyroid cancer was the third most common cancer in Rabat and Casablanca, while it was ranked at the eighth position in our study [10, 11]. Similarly, in men, prostate cancer was the second most common cancer in Rabat and Casablanca while it was ranked at the fourth position in our study [10, 11]. In this study, we found that incidence rates for most cancers are rising in Eastern Morocco. Indeed, the crude incidence rate for all cancers combined has increased from 56.6 to 80.3 per 100,000 per year in females and from 32.3 to 42.6 per 100,000 per year in males during the 2006–2012 period.

Breast cancer was the most common cancer in Eastern Morocco, with a mean age at diagnosis of 48.7 years ±11.4. This result is similar to that observed in the cancer registries of Casablanca (48.1–49.5 years ±11.3) [29, 30]. However, a different picture is observed in Western countries where breast cancer affects older women [31, 32]. The CR of breast cancer has increased from 2006 to 2012 in Eastern Morocco (23 to 36.8 per 100,000). This rising in trend may be explained by the breast cancer national screening program which has been adopted in Morocco for the period 2010–2019 in the context of the National Cancer Prevention and Control Plan [33]. However, there has been a significant increase in the trend before the program had been implemented (2006–2008), suggesting that this rising in trend for breast cancer is linked to one or more of the known risk factors for breast cancer. It is possible that some of the increase is related to declines in fertility, since the number of births has declined from 4.5 in 1987 to 2.2 in 2010 [34]. The rising in trend may also be related to later age marriage, since the mean age at marriage of women has steadily increased from 22.2 years in 1982 to 26.6 in 2010 [34]. Several other risk factors could be involved in the trend, like changes in diet, physical activity, lifestyle, genetic factors, age of menarche, exposure to hormones and breastfeeding.

Colon-rectum cancer was the second most common cancer in males and the third in females in Eastern Morocco. The CR of colon-rectum cancer has increased from 2006 to 2012 in Eastern Morocco in both sexes. This rising incidence trends for colon-rectum cancer may be linked to changes in dietary habits. Indeed, it has been well established that a high calorie diet and rich in animal fats, mostly absorbed in the form of red meat, and with few vegetables and fiber, is associated with an increased risk of colon-rectum cancer. Alcohol and smoking also increase the risk for colon-rectum cancer [35‐37]. Conversely, a diet providing little fat, lots of vegetables and possibly rich in fiber, has a protective effect [38‐42]. In Eastern Morocco, there is still no screening program for colon-rectum cancer. Therefore, the observed rising incidence trend in this cancer in both males and females justifies the need to establish programs for colon-rectum cancer control and prevention in Eastern Morocco.

Lung cancer was the most common cancer in males in Eastern Morocco. The incidence of Lung cancer in males has increased from 2006 to 2012 in Eastern Morocco (5.3 to 8.9 per 100,000). Lung cancer is the leading cancer in males in developing countries. However, it ranks second after prostate cancer in Europe [43]. This is also the leading cause of cancer death [44]. The association between lung cancer and smoking is well established [45‐47]. Therefore, the observed rising incidence trend in lung cancer in Eastern Morocco may be linked to the increase in the prevalence of smoking [48, 49]. Thus, it is important to develop tobacco control measures as soon as possible to avoid future increases in lung cancer in Eastern Morocco.

Nasopharynx cancer was the third most common cancer in males and the sixth among women in Eastern Morocco. In both sexes, nasopharynx cancer has shown a steady decline in incidence throughout the study period. This decreasing trend can be linked to changes in diet, lifestyle or exposure to toxic smoke. Indeed, the association between nasopharynx cancer and smoking, working in conditions with poor ventilation, infection with Epstein Barr virus, and the rich traditional food preservatives has been demonstrated [50‐53]. In males, the age-specific incidence rate of nasopharynx has shown a bimodal distribution with the first peak in children (15–19 years), and the second peak in adults (age group 50–59 years). This result is similar to that observed in the cancer registry of Setif in Algeria (two peaks at 15–24 and 50–59 years) [54] . However, a different picture is observed in the cancer registry of Casablanca, where the first peak was observed earlier (10–14 years age group) [11, 22, 54]. This difference may be explained by the under-representation of childhood cancer in this study because the ROC typically manages adult cancer patients. In females, the incidence rate increased gradually with age and reached a peak in the 55–64 years age group. Such a finding is different from the one reported in Casablanca, where the age-specific incidence rate showed that the incidence rate reached a peak in adults at an earlier age group (40-44 years) [11, 22, 54]. These differences may be explained by a lower prevalence of smoking among females in Eastern Morocco compared to Casablanca. Further studies are needed to determine the causes of these differences.

Cancers are caused by several factors, including genetic, geographical, socioeconomic, and cultural factors [55‐57]. Thus, the epidemiological characteristics of cancer vary from one region to another, and even within the same country. In Tunisia, for example, cancer registries of Sousse, Sfax and northern Tunisia have shown quite different cancer incidence rates [22]. Similarly, the data presented here on cancer patterns in Eastern Morocco are different from those of the Casablanca and Rabat cancer registries [10, 29]. The low socioeconomic status could in part explain the general increase in the incidence of cancer of most major sites in Eastern Morocco during the study period. Indeed, 79% of incident cancer cases registered at the Regional Oncology Center were from urban areas and 21% from rural areas (p < 0.001). Moreover, 83% of patients were unemployed and 85% have no health insurance. It is worth noting that according to the High Commission for Planning, the employment rate for women in eastern Morocco is only 11.1%, compared to 65.7% for men [58]. Therefore, men may be at lower risk due to engaging in occupations requiring greater physical activity. Although occupational differences may explain some of the sex difference, other factors such as diet and hormonal differences must be considered.

In the absence of a cancer registry in Eastern Morocco, it is difficult to understand the epidemiology of this disease and develop programs for cancer control and prevention. Since Hassan II Regional Oncology Center was the only specialized cancer hospital for cancer management in Eastern Morocco during the study period, these results are of great value and provide a valuable tool for cancer control and prevention in Eastern Morocco. Our results confirm the gravity of this problem, and provide epidemiological knowledge about cancer which is necessary for health care planning. This work is of great interest to the health system since any prevention policy cannot be implemented without epidemiological studies and very thorough statistical analysis. Indeed, the rates of many cancers are rising and require the development of effective programs for cancer control and prevention. A better and easier access to cancer care is a priority, given that the majority of patients who are treated in the Regional Oncology Center are unemployed, and do not have medical care coverage. It is also essential to initiate the establishment of a regional cancer registry to allow the surveillance of cancer trends and to plan a program for cancer control and prevention in Eastern Morocco.