Background
Cancer is the second leading cause of death of non-communicable diseases worldwide [
1]. Its prevalence increased by 25.4% between 2007 and 2017, and population ageing contributed about 22% to this increase [
1]. Prevalence and incidence of cancer in people aged 70 years and older were estimated to be about 27.1 and 9.6 million cases in 2017 [
2].
Due to the effects of both, the disease and its usually intensive treatment, patients with cancer have an increased risk of malnutrition. Various cancer-related mechanisms, such as systemic inflammation [
3] and hypoxic stress [
4] affect the patients’ nutritional status. Patients might already present lower dietary intake before anticancer treatment [
5] and in addition, side effects of anticancer therapy, e. g. loss of appetite, dry mouth or nausea that are associated with a lower energy intake [
6]. The prevalence of malnutrition in patients with cancer is described by 26–42% [
7‐
9], and varies between different operationalisations [
10‐
12]. To better reflect the health status of an older patient before treatment decisions are made by oncologists, a (comprehensive) geriatric assessment is recommended [
13‐
15], consisting of several domains such as functional status, cognition, comorbidity or polypharmacy and it is also recommended that it should contain a domain regarding the patients’ nutritional status assessed by validated tools such as the Mini Nutritional Assessment (MNA)® [
15]. A recent study by Kenis et al. could show that components of comprehensive geriatric assessment are prognostic factors (especially functional status and nutritional status) for overall survival in patients with cancer which additionally highlights the need for nutritional assessment [
16]. It was also shown, that (severe) malnutrition is independently associated with mortality risk and decreased tolerance of chemotherapy [
17]. Therefore, early detection and treatment of malnutrition is recommended for the prevention of cancer-related adverse outcomes [
18‐
20].
However, no gold standard for screening and assessment of malnutrition in cancer patients exists. Among 37 malnutrition screening and assessment methods utilized for patients with cancer in clinical practice, in a recent systematic review, the MNA scored highest for the calculated content validity [
21]. This tool is validated to identify persons aged 65 years or older who are at risk of malnutrition or malnourished [
22‐
25].
The MNA is widely used in patients with cancer of all ages [
26], even though it is neither developed specifically for this disease nor for persons younger than 65 years. Both versions, the short-form (MNA-SF) and long-form (MNA-LF), are recommended for screening of nutritional status of older patients in all clinical settings [
27]. For patients with cancer, the use of MNA-SF is recommended by medical oncology societies for older patients with cancer [
28,
29] as well as by practicing oncologists [
30]. A summary of results about the association between MNA and relevant patient outcomes is currently lacking. Thus, our aim was to systematically summarize the existing evidence regarding nutritional status according to the MNA as potential prognostic factor for health and treatment outcomes in cancer patients.
Methods
This systematic review is reported according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement [
31]. A protocol describing the methodological procedure was prepared before the start and is available upon request.
Systematic literature search
A systematic literature search using database specific search strategies was conducted in MEDLINE and EMBASE (via Ovid), the Cochrane Library and CINAHL (via EBSCOhost) in June 2017 for studies published in any language from 1994 (first published version of MNA) onwards. The search was updated twice, in September 2018 and March 2020. Search strategies have been developed by 1 reviewer (GT) and discussed by the working group members (GT, TS, EK and DV) and a librarian. The search strategies included a combination of keywords and MeSH−/ Emtree-terms (e.g. nutritional status, MNA, cancer) (Additional file, table
1). Additionally, reference lists of included studies were searched.
Study selection
Original articles of longitudinal studies reporting a potential association between nutritional status assessed by MNA (any form) at baseline and any health or treatment outcome (e.g. mortality, survival, complications) at a later time point in patients of any age with any type of cancer and anticancer therapy were included. Studies with a cross-sectional design and those not using MNA-assessed nutritional status for predicting health and treatment outcomes were excluded as well as other publication types (e.g. conference abstracts or editorials). Currently, 2 forms of the MNA are available, which were both included. The short-form (SF) consisting of 6 items (A-F), first developed in 2001 [
24] and revised in 2009 (range 0–14 points; 0–7 points: malnourished; 8–11 points: at risk of malnutrition and 12–14 points: normal nutritional status) [
23], and the long-form (LF) or “full MNA” consisting of additional 12 items (G-R) [
22,
25] (range 0–30 points; 0–17 points: malnourished; 17–23.5 points: at risk of malnutrition and 24–30 points: normal nutritional status).
Titles/abstracts and full texts were screened by 2 reviewers (GT, TS) independently. Conflicts were solved by discussion or by a third reviewer (EK).
Two reviewers (GT, TS) independently extracted the following data using a piloted extraction form:
a) Study characteristics: first author, year of publication, country, sample size.
b) Participant characteristics: age, sex, type of cancer, cancer stage, anticancer therapy (e.g. chemotherapy).
c) Malnutrition screening tool and result: MNA form (MNA-SF or -LF), MNA result as reported by the authors (prevalence of malnutrition, risk of malnutrition and well-nourished patients and/or mean/median score.
d) Outcome characteristics: follow-up time, prevalence or incidence of any reported outcome at/during follow-up; results on prognostic effects (e.g. odds ratios (OR), hazard ratios (HR) for respective outcome (e.g. mortality)) from multivariable analyses.
Assessment of risk of bias
Two reviewers (GT, EK) independently assessed the risk of bias (RoB) of each included study using a specified version of the QUIPS-tool [
32] (Additional file, table
2). We predefined a set of core confounders (cancer stage, type of cancer, type of therapy, sex, age, performance status, co-morbidity) and dropped the first item ‘definition of the prognostic factor’ of the ‘
prognostic factor measurement’ domain since we were interested in nutritional status according to MNA as the only prognostic factor. The item ‘
valid and reliable measurement of prognostic factor’ was rated as having a low risk of bias when the study reported all 3 MNA-categories or the MNA-score.
The domains study participation, study attrition, prognostic factor measurement, outcome measurement, study confounding and statistical analysis and reporting were rated with either low, moderate or high RoB and are separately presented for each study. Conflicts were solved by discussion or a third reviewer (DV).
Data synthesis
Reported outcomes were classified in 7 categories: (a) mortality/ poor overall survival, (b) progression-free survival and time to progression, (c) treatment maintenance or duration, (d) adverse treatment outcomes (toxicity, complications), (e) functional status / decline and (f) quality of life and (g) other outcomes.
Due to a high heterogeneity of patient populations and reported outcomes meta-analyses were not possible.
Discussion
In this systematic review, we investigated the prognostic significance of baseline nutritional status according to MNA regarding health and treatment outcomes in patients with cancer. In 56 studies included in our review, we found that, based on a moderate to high risk of bias, poor nutritional status is associated with a significantly higher risk for mortality / poor overall survival (22/27 studies), longer progression-free survival / time to progression (3/5 studies), worse treatment maintenance (5/8 studies) and (health-related) quality of life (2/2 studies) in multivariable analyses. Adverse treatment outcomes (1/7 studies) and functional decline (1/3 studies) were not significantly predicted by MNA in adjusted analyses while other outcomes were not investigated in multivariable analyses.
The
MNA was originally developed to identify patients 65 years or older at risk of malnutrition irrespective of a specific disease [
23,
25].
The
prevalence of malnutrition, risk of malnutrition or their combination was 0–41%, 7–67%, and 28–67%, respectively – however not reported in all studies (Additional file
1, Table
1). We could not identify a trend for a higher or lower prevalence of malnutrition in studies including patients with a specific kind or stage of cancer as documented in a large cohort study from Italy including 1952 patients with various types and stages of cancer. There, a prevalence for malnutrition of 8.7% and risk of malnutrition of 42.4% was reported for all patients, but when stratified for cancer stage, both MNA-categories, malnutrition and risk of malnutrition were significantly higher in stage IV compared to stage I-III cancer [
88]. A meta-analysis of studies including hospitalized patients older than 60 years with any disease, reported a prevalence for malnutrition of 22.0% (95%-CI: 18.9–25.2) and risk of malnutrition 45.6% (95%-CI: 42.7–48.6) [
89]. Recently, a consensus for the diagnosis of malnutrition, the Global Leadership Initiative on Malnutrition (GLIM)-criteria, was published [
90] and a few studies regarding nutritional status in patients with cancer are available. Prevalence rates for malnutrition according to GLIM were reported between 25.8 and 80% - depending on the criteria which were used for the diagnosis according to GLIM [
91‐
93].
We could show that the
chance for mortality was higher in patients being malnourished and at risk of malnutrition compared to well-nourished patients in the majority of studies (Table
2, Additional file table
3a). This is in line with 3 recently published systematic reviews also addressing the relation between malnutrition and mortality in patients with cancer [
94‐
96]. While their approaches and search strategies differed with respect to inclusion of other screening tools and prespecified outcomes, there is an overlap of included MNA-studies. However, we could identify additional studies, so that our systematic review adds further evidence for the relationship between nutritional status assessed by MNA and mortality. Other systematic reviews with focus on a specific type of cancer (pancreatic, gastrointestinal) [
97‐
99] or cancer stage (advanced) [
100] reported that mortality risk / overall survival is predicted by nutritional status according to low body mass index, the Prognostic Nutritional Index, Controlling Nutritional status and phase angle [
97‐
100]. For the Patient-Generated Subjective Global Assessment, which is also often used and recommended for nutritional screening in patients with cancer, several primary studies investigated the association with mortality/ overall survival and showed conflicting results with a majority of studies predicting a higher risk [
101‐
104]. Two studies investigated the association between malnutrition according to the GLIM-criteria and mortality/ poor survival and both could show significant results [
91,
92]. Future studies should investigate the application and prognostic abilities of these criteria. Additionally, an analysis including several cohorts of patients with cancer could show that the risk for mortality was higher in patients with lower body mass index and higher weight loss [
105]. In one study (which was excluded), machine learning algorithms were used to predict early death in older patients with cancer [
106]. Questionnaire items from the comprehensive geriatric assessment were selected by artificial intelligence and the MNA-SF remained in the predictive model. Such studies might be used in future to gain further knowledge of the prognostic factors in patients with cancer. Regarding other diseases, a meta-analysis found nutritional status according to MNA being predictive for mort ality in patients with heart failure [
107].
Besides mortality risk,
time to progression and progression-free survival are often used endpoints in clinical trials to evaluate the efficacy of anti-cancer treatment, since the treatment intention is either curation or a longer survival with a higher quality of life [
108], but were only rarely investigated in relation to MNA. We found evidence that a poor MNA-result is predictive for a shorter time to progression / progression-free survival (Table
2, Additional file table
3b). These endpoints are mostly not clearly defined, but it is generally agreed among experts that time to progression reflects the time to cancer progression whereas progression-free survival also includes death from any cause [
109,
110]. However, it is discussed whether these endpoints are meaningful outcomes in cancer research, since a recent systematic review, including about 14,000 adult patients until 93 years with various kinds of cancer, showed that a prolonged progression-free survival is not associated with a higher health-related quality of life [
111]. The association between a poorer nutritional status and a higher risk for a shorter progression-free survival was also shown in a recent meta-analysis investigating the prognostic ability of the Prognostic Nutritional Index in patients with hepatocellular carcinoma [
112]. For other tools, primary studies found a shorter progression-free survival significantly predicted by nutritional status assessed by the Geriatric Nutritional Risk Index or the Controlling Nutritional Status Score in different types of cancer [
113,
114], but systematic reviews are lacking.
When patients with cancer had poor MNA at baseline,
treatment maintenance was poorer but treatment duration (1 study) was not shorter (Table
2, Additional file table
3c). Main reasons for poorer maintenance were toxicity, cancer progression and insufficient therapeutic effect [
33‐
36].
In included studies investigating
toxicity as a separate outcome, a significant association with MNA-result at baseline was not found. Only non-hematologic toxicity was predicted by a poorer nutritional status according to MNA in 1 study [
48] (Table
2, Additional file table
3d). Also,
complications after surgery were not predicted by MNA (Table
2, Additional file table
3d). This is in line with results of other systematic reviews including patients with various kinds of cancer that showed a lower chance of treatment-related adverse events by geriatric assessment components only according to functional status, cognition and depression but not by nutritional status according to various definitions [
95,
115,
116]. In contrast, in adult patients undergoing joint arthroplasty or hip fracture surgery, malnutrition defined by serologic markers (e.g. albumin, lymphocyte count, transferrin) was predictive for a higher risk of postoperative outcomes, such as wound complications [
117,
118]. One study in older hip-fracture patients showed that patients with (risk of) malnutrition patients – according to MNA-SF – were at higher risk for postoperative delirium compared to well-nourished patients [
119]. In another study, a significant association between malnutrition and chemotherapy related toxicity could be showed for the Patient-Generated Subjective Global Assessment but not for the Nutritional Risk Index [
103]. To clarify these conflicting results, further studies are required in patients with cancer.
Only 1 of 3 studies predicted functional decline in basic activities of daily living by poor MNA-result and all 3 studies failed to predict a decline in instrumental activities of daily living (Additional file, table
3e). In older hospitalized patients with various diseases, nutritional status according to Short Nutritional Assessment Questionnaire was also not related to functional decline [
120] but a moderate association was found for MNA in older people from different settings (i.e. community-dwelling, acute, subacute or residential care) [
121]. A systematic review of studies including older hospitalized patients with various diseases revealed that baseline functional and cognitive status as well as social support were more important to predict functional outcomes than nutritional status [
122]. These results demonstrate the need for further studies regarding the association between MNA and functional decline in patients with cancer.
For
(health-related) quality of life, 1 study that was identified by our systematic literature search was only small, including patients with prostate cancer. Only 2% were malnourished and unfortunately no adjusted analysis was reported [
57]. Two other studies that we also included could show a lower chance for a decline in health-related quality of life for patients with (risk of) malnutrition [
45,
75] (Table
2, Additional file table
3f). This finding might be explained by the already poor quality of life at baseline or, in other words that after anticancer therapy the chance for an improvement in quality of life was higher for patients with (risk of) malnutrition compared to well-nourished patients with already better quality of life.
Regarding length of hospital stay (2 studies), fatigue, falls and unplanned admissions (1 study each), only a very small number of studies investigated the association with baseline MNA with no multivariable analyses, and more studies are needed also in this regard to draw any conclusion.
Several limitations of the included studies need to be considered. First, risk of bias was judged as moderate to high in all included studies, which is in contrast to other systematic reviews reporting a low to moderate risk of bias [
94,
95]. Our rating is mainly explained by insufficient consideration of potential confounders – which have been predefined by 2 reviewers (cancer stage, type of cancer, sex, age, performance status, co-morbidity) – in multivariable analyses of primary studies to minimize the risk of residual confounding which is generally one of the most relevant limitations of observational studies [
123‐
125]. Second, in several studies [
33,
34,
37,
42,
53,
56,
58,
61,
64,
68,
74,
80,
82,
87], effect estimates had relatively wide confidence intervals and this imprecision should be considered when interpreting these results. Reasons for imprecisions might be an insufficient number of participants or malnourished patients. Third, follow-up times differed widely between the studies and only a few defined or reported a specific time point for outcome assessment. Mostly only vague information about follow-up times, such as a mean overall survival, was provided. Thus, conclusions for a specific time-frame cannot be drawn.
Furthermore, we included articles that report on study populations recruited from the same hospitals within a recruitment time from 2004 to 2010 [
33‐
37]. All patients were treated by chemotherapy. We did not exclude one of these studies, since 2 publications focused on a specific type [
33,
37] and the other 3 publications included various types of cancer [
34‐
36] with 1 study focusing on patients with different types of non-Hodgkin Lymphoma [
34] and 1 study with a shorter recruitment period [
35]. Although reported results differed, this overlap should be kept in mind.
Strengths
Main strength of this systematic review is its strict methodology which followed the PRISMA guideline [
31]. We conducted an extensive literature search without any language restrictions and did not specify search terms for outcomes to integrate all health and treatment outcomes that were investigated in primary studies. Each review step (screening, data extraction and RoB assessment) was piloted and performed by 2 reviewers independently. Additionally, we focused on 1 screening tool to minimize heterogeneity due to assessment. As part of the assessment of RoB, our rating of the confounding domain was strict and other reviewers might rate differently – but this is a general problem with RoB rating.
Limitations
The databases we used have their major focus on journals from the US and Europe and journals from other regions might not have been identified by our exhaustive systematic literature search. Therefore, language bias cannot be excluded although we did not restrict our search to specific languages.
The large heterogeneity of included studies regarding samples, treatments and outcome assessments should also be considered when interpreting our results. However, despite this heterogeneity, a rather stable relation between MNA result and several outcomes was observed.
Implications for research
Large, prospective and registered cohort studies should be conducted to strengthen our results, which are based on heterogeneous samples and outcomes. In addition, future studies that investigate the comparison of the prognostic ability of different nutritional screening/ assessment tools (such as the MNA, the Patient-Generated Subjective Global Assessment or the Nutritional Risk Screening 2002) or criteria (such as the GLIM-criteria) are needed. Publications should follow the respective guidelines provided by the Enhancing the QUAlity and Transparency Of health Research (EQUATOR) network (
https://www.equator-network.org/reporting-guidelines/) to further standardize reporting of studies.
Implications for practice
Based on our observation of negative health and treatment outcomes in patients with poor MNA-result and in light of available effective nutritional interventions, health care professionals should be aware of nutritional status and should support and engage patients to improve their nutritional status before and during anti-cancer therapy.
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