A prospective study examining links between diet quality and survival of patients with metastatic colorectal cancer (CRC) found no link between diet at the initiation of first-line treatment and overall survival.
For the study, Erin Van Blarigan, ScD, of the University of California San Francisco, and colleagues assessed “validated food frequency” questionnaires completed by 1,284 of 2,334 patients (55.0%) with metastatic CRC enrolled in the Cancer and Leukemia Group B (Alliance)/Southwest Oncology Group 80405 trial. The results, published online in JAMA Network Open, found no significant association in overall survival and any of five dietary patterns:
- Alternative Healthy Eating Index (AHEI), which is scored from 0 to 110 and is based on vegetables (excluding potatoes), fruits, whole grains, nuts and legumes, long-chain n-3 fatty acids, polyunsaturated fatty acids, sweetened beverages and juice, red and processed meat, trans fat, sodium, and alcoholic drinks
- Alternative Mediterranean Diet (AMED), which is scored from 0 to 9 and is based on vegetables, fruits, nuts, whole grains, legumes, fish, ratio of monounsaturated to saturated fat, red and processed meat, and alcohol
- Dietary Approaches to Stop Hypertension (DASH) diet, which is scored from 0 to 45 and is based on fruits, vegetables, nuts and legumes, low-fat dairy, whole grains, sodium, sweetened beverages, red and processed meats, and sweets and desserts
- The Western dietary pattern, characterized by higher intake of dairy, refined grains, condiments, red meat, and sweets and desserts
“Making lifestyle changes is hard, especially when you are dealing with cancer diagnosis and treatment,” Van Blarigan told MedPage Today. “Patients may wish to focus their energy 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 suggests that patients should really prioritize exercise during and after their cancer treatments.”
Overall, none of the diet scores or patterns examined were associated with survival in metastatic CRC, the investigators reported. “We observed an inverse association between the AMED score and risk of death (HR quintile 5 [Q5] vs quintile 1 [Q1] 0.83, 95% CI 0.67-1.04, P=0.04 for trend), but point estimates were not statistically significant. Additionally, the Western diet pattern was associated with longer survival in individuals with KRAS variant tumors (HR Q5 vs Q1 0.50, 95% CI 0.32-0.77) but not those with wild-type tumors (HR Q5 vs Q1 0.95, 95% CI 0.68-1.33, P=0.02 for interaction).”
“None of the other diet scores or patterns were associated with survival, overall or in subgroups, and the results did not change when patients who died within 90 days after administration of the [questionnaire] were excluded,” the team noted.
Writing in an accompanying commentary, Cindy Kin, MD, MS, of Stanford University School of Medicine in California, pointed out that although a Western diet, high in red meat and saturated fats, has been linked to the development of colorectal cancer, the new study addresses the less well-studied area of diet quality and outcomes in CRC, particularly for those with metastatic disease.
“Most oncologists do talk about healthy diets to their patients who are actively undergoing cancer treatment,” Kin wrote. “How effective such conversations are in affecting actual lifestyle changes is unclear … More studies are necessary for understanding the associations of diet with outcomes during and after treatment. Answering this question is critical for formulating actionable diet interventions to best support these patients through treatment and to optimize their outcomes.”
Van Blarigan also noted that studies with repeated measures of diet are needed, and pointed out that her team’s study looked at dietary patterns and scores, which look at many factors of diet together.
“It remains possible that specific dietary factors are important,” she said. “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.”
One limitation, she added, was that the study included mostly people who identified as being non-Latinx white, so research is needed in more racially/ethnically diverse populations.
The study was supported by the National Cancer Institute, and funds were also provided by Bristol Myers Squibb, Genentech, Pfizer, and Sanofi.
Van Blarigan reported receiving grants from the National Cancer Institute during the conduct of the study; co-authors reported financial relationships with various companies.
Kin reported no conflicts of interest.