Nut Consumption Linked to Survival Benefit in Colon Cancer

Charles S. Fuchs, MD

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), according to results from the CALGB 8903 study published in the Journal of Clinical Oncology.

The association between total nut intake and improved outcomes was consistent across other known or suspected risk factors for cancer recurrence and mortality.

“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,” wrote Charles S. Fuchs, MD, Yale Cancer Center, and colleagues. “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) enrolled in the CALGB 89803 adjuvant therapy trial for stage III colon cancer that compared weekly fluorouracil and leucovorin versus weekly irinotecan, fluorouracil, and leucovorin from April 1999 to May 2001.

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

An ounce of tree nuts and peanuts was considered 1 serving. 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).

Investigators also considered the possibility that nut intake may be a marker of dentition and oral health. To address this issue, they ran the models using a new reference group that combined the lowest intake categories—never and ≤1 serving per month—and found that, again, the results remained largely unchanged. Individuals reporting 2 or more servings of nuts per week demonstrated an improvement in DFS compared with the new reference group (HR, 0.57; 95% CI, 0.38-0.87; P_trend = .03).

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.