Patient QoL is an extremely important outcome measure for cancer patients. How patients feel, physically and emotionally, while they are fighting cancer can have an enormous effect on their ability to carry out normal daily functions as well as on their interpersonal relationships and their ability to work.
Cancer and its treatment affects the nutritional status of patients by altering their metabolic function and reducing their food intake.[5, 6] Research has proven that malnutrition is a predictor of morbidity in advanced cancer; therefore, malnutrition is also likely to assume a significant role in patients’ QoL. The present study aimed to systematically review the relationship between nutritional status and QoL in cancer patients. A total of 26 original studies were included in this review. Of the 26 studies, 6 investigated the correlation in head and neck cancer patients, 8 in gastrointestinal cancer patients, 1 in lung cancer patients, 1 in gynecologic cancer patients and 10 in heterogeneous cancer populations.
Better nutritional status was associated with better QoL in all 6 studies of head and neck cancer patients with each study identifying different reasons for the correlation. One study reported that weight loss in some patients was related to loss of speech and swallowing capabilities, which may have affected patients’ ability to take food by mouth. Another study concluded that weight loss of more than 10% had significant impact on QoL scores at time of diagnosis and that it seemed to significantly worsen global QoL, fatigue and pain. The same study advised that patient weight loss should be limited as much as possible starting at diagnosis and continuing until six months after treatment. Another study showed that patients in the ≥10% weight-loss group reported extreme problems (>80 points) with dry mouth and sticky saliva at 3 months, 1 year and 3 years after diagnosis. This effect was attributed, on the basis of previous studies, to the fact that this patient population was comprised of more people who lived alone, more smokers/ex-smokers, a higher percentage of patients with stage III to IV disease (95% vs 50%), a higher percentage of patients with pharyngeal cancer, and more patients who received chemotherapy. In summary, these 8 studies indicate that poor nutritional status, measured primarily using weight loss, was a strong predictor of patient QoL, measured primarily through EORTC QLQ-C30, in head and neck cancer patients.
All 8 studies that explored the association between nutritional status and QoL in gastrointestinal cancer patients concluded that better nutritional status was associated with better QoL. One study theorized that an inflammatory response may contribute to weight loss in advanced gastrointestinal cancer patients by increasing energy expenditure and the turnover of specific amino acids, which reprioritizes the body’s protein metabolism away from peripheral tissues and toward the liver. This process appears to contribute to the preferential loss of protein (in particular, skeletal muscle) in such patients. This in turn may be a cause of appetite loss and lowered QoL in gastrointestinal cancer patients.
The lone study that reported a significant relationship between nutritional status and QoL in lung cancer patients speculated that the relationship between pain and more than 5% prior weight loss may simply be a result of more advanced disease, as there were a greater number of weight loss patients in this group who had been diagnosed with stage IV disease. The lone study that explored the association between nutritional status and QoL in gynecological cancer patients indicated that nutritional status (in terms of BMI) was significantly associated with QoL. More than 70% of the patients were either overweight or obese suggesting that obesity is another form of malnutrition that is often overlooked in clinical settings, and can have a negative impact on patient QoL.
Of the 10 studies that investigated the relationship between nutritional status and QoL in a heterogeneous cancer population, eight concluded that nutritional status was significantly associated with QoL, one found nutritional status to be significantly associated with QoL only for high-risk patients, and one found no association between the two. Of the eight studies reporting significant association, one reported that although an association between malnutrition and impaired QoL was observed in all sub-groups of patients, it was not possible to identify which was the cause and which was the consequence: weight loss or QoL. The authors attributed this issue to the study design (transversal study). Another study also inferred that it was not possible to conclude which came first – insufficient food intake, decreased QoL or weight loss – although the authors did establish that the three variables were interdependent..
Overall, among the 26 studies reviewed in this article, 24 concluded that better nutritional status was associated with better QoL, one study showed that better nutritional status was associated with better QoL only in high-risk patients, and one concluded that there was no association between nutritional status and QoL.
The majority of the studies reviewed in this article used weight loss (expressed as weight loss or unintentional weight loss or percentage of weight loss) as the tool for assessment of nutritional status, either exclusively[18, 19, 26–28, 31–33] or in combination with other methods.[8, 12, 22] The results described by these papers suggest that weight loss is a good prognosticator of QoL irrespective of the type of cancer for a number of reasons. One, weight loss is a common feature of advanced cancer due to patient distress and loss of independence. Weight loss is a known cause of morbidity and mortality in cancer patients that also decreases patient tolerance to both radiotherapy and chemotherapy. Weight loss as low as 5% can alter important, measurable physiological parameters such as immune response, lung and cardiac function tests and autonomic autoregulation. More than 10% weight loss at diagnosis has a great impact on QoL scores. A total weight loss of ≥ 20% significantly correlates with treatment interruption, infections, early mortality, hospital re-admission rate after treatment completion as well as survival. Recent work suggests that an inflammatory response might contribute to the weight loss in advanced gastrointestinal cancer patients by increasing energy expenditure and the turnover of specific amino acids, which reprioritizes the body’s protein metabolism away from peripheral tissues and toward the liver. This process apparently contributes to the preferential loss of protein (in particular, skeletal muscle) in such patients. The reprioritization of metabolism may also impact patient appetite and, along with it, the QoL of gastrointestinal cancer patients. There is evidence in the literature reviewed that the use of “percentage weight loss since the start of the illness” is a relatively objective measure, although the patient’s usual or “normal” weight is often only approximately known. On the other hand, percentage weight loss does not appear to account for the kinetics of weight loss, presence of edemas, water retention and clinical-biological effects. On the contrary, SGA is the only malnutrition screening tool recommended by the ASPEN board of directors. SGA is a simple, easy-to-apply and cost-effective method that has been validated for diverse groups of patients. SGA is one of the better available assessment methods, not only because it is patient centred and incorporates clinical history and physical examination, but also does not require laboratory testing or medical imaging exams.[36, 37] Reliable SGA grading, however, depends on collection of correct history and physical observation and requires a skilled dietician to carry out the assessment. Nutrition assessment tools such as the scored PG-SGA enable nutritional status to be assessed quickly, nutrition impact symptoms identified and appropriate nutrition support implemented. An advantage of the PG-SGA as a nutrition assessment tool is that the score can be used as an outcome measure in nutrition intervention studies as it may be more sensitive to changes in nutritional status than the global SGA rating. Also, by performing serial measurements, the change in the PG-SGA score may be used to demonstrate subtle changes in nutritional status.
The majority of the studies reviewed here used EORTC-QLQ-C30 to assess patient QoL, either exclusively[2, 8, 10, 22, 24, 26, 28, 31, 32] or in combination with other QoL tools.[7, 12, 18, 19, 23, 27] The EORTC QLQ-C30 questionnaire is a validated instrument for assessing QoL in patients with cancer. It is usually completed by self-assessment[12, 27] and covers more items and scales, identifies more domains and specific complaints, and assesses cancer and radiotherapy specific symptoms, and is, therefore, a more comprehensive and sensible measure than some others.
Collectively, the studies reviewed in this article suffered from certain limitations. Three studies involved small sample sizes, which made comparisons and statistical analyses difficult.[5, 17, 24] Non-responders contributed toward bias in one study, while another made no assessment of inter-rater reliability of the users of SGA and BIA. These studies minimized this bias by using only BIA-trained dieticians. Two studies reported exclusion of patients with physical, cognitive, language or emotional problems that prevented them from completing the respective QoL questionnaires.[2, 5] Another study was a secondary analysis and was not designed as a nutrition trial. As a result, some of the nutritional parameters included in the survey were limited. Also, there was significant attrition between T2 and T3 and, apparently, more stage IV patients were lost to attrition. Thus, the prevalence of nutrition impact symptoms in these patients may have been underreported. One study reported that its outcome data may have been misclassified, but then ruled out the probability of error on the grounds that 1) the analysis of self-reported preoperative body weight compared with body weight measured by surgical staff before operation showed good validity and 2) that the questionnaires covering nutritional issues had been previously validated.
Like most other systematic reviews of the literature, this review suffers from potential publication bias. In general, this bias exists because studies that report positive associations are more likely to be published. Therefore, it is possible that studies containing valuable data may not have been published and have gone undetected. Since we restricted this systematic review to studies published in English, it is possible that language bias may have affected our conclusions. Finally, our review simply focused on the relationship between nutritional status and QoL in cancer, which does not by any means imply causation. As a result, a logical next step would be to systematically review the available literature, if any, to investigate whether nutritional intervention can have a favorable impact on QoL outcomes in cancer patients. Despite these limitations, our review and analysis of the extensive available literature demonstrates a strong association between nutritional status and QoL in cancer.
Also as a result of our review, we have identified new avenues for further research in this area. One is to identify the best management practices for timing of nutritional assessment and intervention in cancer patients as, currently, there is no consensus on how to manage patients based on any of the nutritional metrics reviewed here. Nonetheless, this review of the literature provides a strong rationale for devising such standards of practice and testing their value in controlled clinical studies. All clinical manifestations of malnutrition should be included, as well as specific situations where a causative relationship with QoL is apparent.
Our review of the current literature supports the hypothesis that nutritional status is a strong predictor of QoL in cancer patients. It also supports an approach to cancer treatment that takes all aspects of the patient’s life into account. Further, the current literature supports the implementation of the ASPEN guidelines for oncology patients, which include nutritional screening, assessment, and intervention as appropriate. Correcting malnutrition in cancer patients can have a significant positive impact on their QoL.