Diet Quality May Not Impact Survival in Patients with Metastatic Colorectal Cancer

The quality of a diet at the start of first-line treatment for metastatic disease may not impact overall survival in patients with metastatic colorectal cancer, according to study results published in JAMA Network Open.

“The results from this observational study suggest that overall dietary habits at the start of treatment for metastatic disease may not be associated with survival in people with metastatic colorectal cancer,” said Erin L. Van Blarigan, ScD, associate professor in the department of epidemiology and biostatistics at the University of California, San Francisco, in an interview with CURE®. “Strong consistent data suggest that diet is a risk factor for developing colorectal cancer, and that diet after diagnosis may be associated with survival in people with nonmetastatic disease. Together, these data suggest that dietary interventions to improve colorectal cancer survival may need to be conducted earlier in the disease process before metastases have been detected.”

In this prospective analysis, the study authors assessed data from 1,284 patients (median age, 59 years; 41% women; median body mass index, 27.2 kg/m2) with untreated metastatic colorectal cancer. All patients were enrolled in the Cancer and Leukemia Group B and Southwest Oncology Group 80405, a trial sponsored by the National Cancer Institute which assessed first-line therapy for metastatic or advanced colorectal cancer.

Within four weeks of starting treatment, patients completed a food frequency questionnaire, which assessed the intake of approximately 130 items during a three-month period. The study authors analyzed three diet quality scores and two dietary patterns, including the following:

• the Alternative Health Eating Index, which is based on fruits, vegetables (except for potatoes), nuts and legumes, whole grains, polyunsaturated fatty acids, long-chain n-3 fatty acids, red and processed meat, sweetened beverages, alcoholic drinks, sodium and transfat;
• the Alternate Mediterranean Diet, which included fruits, vegetables, whole grains, nuts, fish, legumes, red and processed meat, ratio of monounsaturated to saturated fat, and alcohol;
• the Dietary Approaches to Stop Hypertension, which is based on vegetables, fruits, low-fat dairy, nuts and legumes, sodium, whole grants, red and processed meats, sweetened beverages, sweets and desserts;
• the Western dietary pattern, characterized as a higher intake of refined grains, dairy, red meat, condiments, desserts and sweets; and
• the prudent pattern, characterized as a high intake of legumes, vegetables and fruit.

The primary outcome in this study was all-cause death. Data focused in this area were collected from 2005 until January 2018.

During a median follow-up of 73 months, 86% of patients died, the majority of which (89%) were deaths from colorectal cancer. Patients who adhered to the Alternate Mediterranean Diet had a lower risk for death compared with those who did not adhere to this diet, although these estimates were not statistically significant. This association was not observed in the other diets assessed in this study.

“Making lifestyle changes is hard, especially when you are dealing with cancer diagnosis and treatment,” said Van Blarigan. “Patients may wish to focus their energy during therapy on making changes that are most likely to be helpful. Data on diet and exercise in people with metastatic colorectal cancer are very limited, but the information we have right now suggest that patients should prioritize exercise during and after their cancer treatments.”

Van Blarigan added that despite these findings, patients should not dismiss the importance of a healthy diet.

“Our study had only one measure of diet assessed at the start of treatment for metastatic colorectal cancer,” said Van Blarigan. “Given that diet can change over time, studies with repeated measures of diet are needed. We also looked at overall dietary patterns and scores, which look at many factors of the diet together. It remains possible that specific dietary factors are important. For example, our team recently reported that patients in this same cohort who drank coffee had a longer survival compared to people who did not drink coffee.”

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