Diets Rich in Nuts Improve Survival Rates in Patients with Colon Cancer

According to results from a recent study published in the Journal of Clinical Oncology, patients with stage III colon cancer who ate at least 2 servings of nuts per week had superior disease-free survival (DFS) and overall survival (OS).

Additionally, the association between nut intake and outcome improvement was consistent across other known or suspected risk factors for mortality and cancer recurrence, as well.

Charles S. Fuchs, MD, of the Yale Cancer Center, and colleagues write, “This prospective study of patients with stage III colon cancer suggests that a diet with increased nut consumption is associated with a significant reduction in cancer recurrence and mortality.” Fuchs goes on, “Although the findings of our observational study do not establish causality, the results offer further support of the role of diet and lifestyle as modifiable risk factors of outcomes in patients with colon cancer.”

After a median follow-up of 6.5 years, the hazard ratio (HR) for DFS in those who consumed ≥2 servings of nuts per week was 0.58 (95% CI, 0.37-0.92; P_trend = .03) and the HR for OS was 0.43 (95% CI, 0.25-0.74; P_trend = .01). In subgroup analysis, the apparent benefit was confined to tree nut intake (HR for DFS, 0.54; 95% CI, 0.34-0.85; P_trend = .04; HR for OS, 0.47; 95% CI, 0.27 to 0.82; P_trend = .04).

Researchers also observed a trend toward improved relapse-free survival (RFS) that did not reach statistical significance (HR, 0.70; 95% CI, 0.42-1.16; P_trend = .15).

Patients in this prospective cohort (n = 826) completed semiquantitative food frequency questionnaires that included 131 food items, vitamin and mineral supplements, and open-ended sections for other supplements and foods not specifically listed. Participants were asked how often, on average, over the previous 3 months they consumed a specific food portion size, with up to 9 possible responses ranging from never to ≥6 times per day.

Questionnaire 1 was administered 4 months after surgery, midway through adjuvant therapy. Questionnaire 2 (Q2) was administered 14 months after surgery, 6 months after completion of treatment.

One serving equals one ounce of tree nuts and/or peanuts. Total nut intake was calculated as the weighted proportional summation of tree nuts and peanuts. Investigators similarly assessed self-reported peanut butter intake. However, there was no association between peanut butter intake and DFS (P_trend = .15), OS (P_trend = .12), or RFS (P_trend = .09).

The primary analyses excluded patients who developed cancer recurrence or died within 60 days of completing Q2 to correct for the possibility that changes in dietary habits could reflect occult cancer or impending death. To further address this issue, investigators repeated the models after excluding recurrences or deaths within 180 days of Q2 completion (n = 783) and again found the results were largely unchanged (HR, 0.54; 95% CI, 0.32-0.89; P_trend = .02).

Fadelu T, Zhang S, Niedzwiecki D, et al. Nut consumption and survival in patients with stage III colon cancer: results from CALGB 89803 (Alliance) [published online February 28, 2018]. J Clin Oncol. doi: 10.1200/JCO.2017.75.5413.