Plant-based diet and survival among patients with metastatic colorectal cancer
En Cheng, Fang‐Shu Ou, Clare A. Gatten, Chao Ma, Alan P. Venook, Heinz‐Josef Lenz, Eileen M. O’Reilly, Peter T. Campbell, Chaoyuan Kuang, Bette J. Caan, Charles D. Blanke, Kimmie Ng, Jeffrey A. Meyerhardt
Abstract
BACKGROUND: A plant-based diet is associated with better survival among patients with nonmetastatic colorectal cancer (CRC), but its association in metastatic CRC is unknown. METHODS: Using an National Cancer Institute-sponsored trial (CALGB/SWOG 80405), we included 1284 patients who completed validated food frequency questionnaires at the initiation of metastatic CRC treatment. We calculated 3 indices: overall plant-based diet index (PDI), which emphasized consumption of all plant foods while reducing animal food intake; healthful plant-based diet index (hPDI), which emphasized consumption of healthful plant foods such as whole grains, fruits, and vegetables; and unhealthful plant-based diet index (uPDI), which emphasized consumption of less healthful plant foods such as fruit juices, refined grains, and sugar-sweetened beverages. We estimated the associations of 3 indices (quintiles) with overall survival (OS) and progression-free survival (PFS) using multivariable Cox proportional hazards regression. RESULTS: We observed 1100 deaths and 1204 progression events (median follow-up = 6.1 years). Compared with the lowest quintile, patients in the highest quintile of PDI had significantly better survival (hazard ratio [HR] for OS = 0.76 [0.62-0.94], Ptrend = .004; PFS = 0.81 [0.66-0.99], Ptrend = .09). Similar findings were observed for hPDI (HR for OS = 0.81 [0.65-1.01], Ptrend = .053; PFS = 0.80 [0.65-0.98], Ptrend = .04), whereas uPDI was not associated with worse survival (HR for OS = 1.16 [0.94-1.43], Ptrend = .21; PFS = 1.12 [0.92-1.36], Ptrend = .42). CONCLUSIONS: Our study suggests that a plant-based diet, especially when rich in healthful plant foods, is associated with better survival among patients with metastatic CRC. The cause of survival benefits warrants further investigation.