Abstract 2200: Plant-based diet and survival among patients with metastatic colorectal cancer: Findings from CALGB/SWOG 80405 (Alliance)

Abstract Background: Plant-based diet is recommended by multiple cancer survivorship guidelines and was reported to be associated with better survival among patients with non-metastatic colorectal cancer. However, the association between plant-based diet and survival in metastatic colorectal cancer is unknown. Methods: Using an NCI-sponsored systemic therapy trial conducted from 2005 to 2015 (CALGB/SWOG 80405), we included 1,279 patients who completed validated food frequency questionnaires at the initiation of treatment for metastatic colorectal cancer. To emphasize different impact of healthful plant foods, less healthful plant foods, and animal foods, we used 18 food groups to calculate three plant-based indexes (ranges: 18-90 points): overall plant-based diet index (PDI), healthful plant-based diet index (hPDI), and unhealthful plant-based diet index (uPDI). The primary outcome was overall survival, and the secondary outcome was progression-free survival. We estimated the associations of three indexes (quintiles) with survival using multivariable Cox proportional hazards regression. Results: Of 1,279 patients (median follow-up: 6.1 years), mean (SD) age at diagnosis was 58.8 (11.7) years, 57.4% were men, 85.6% were White, and 1,096 deaths and 1,201 events of progression occurred. The mean (SD) points of three indexes were 51.2 (6.3) for PDI, 51.1 (6.7) for hPDI, and 51.2 (8.1) for uPDI. Compared to the lowest quintile (Q1), the highest quintile (Q5) of PDI was significantly associated with better overall survival (HR: 0.80 [0.65-0.99]) and progression-free survival (HR: 0.80 [0.65-0.98]). Similar findings were observed for hPDI, but uPDI was not significantly associated with worse survival. Conclusions: Our findings suggest that plant-based diet is associated with better survival among patients with metastatic colorectal cancer, and plant-based dietary interventions should be considered for future trials in metastatic colorectal cancer. Table. Adjusted Associations of Plant-Based Diet with Survival in Metastatic Colorectal Cancer Q1 Q2 Q3 Q4 Q5 P for trend Overall Survival PDI 1.00 0.96 (0.80-1.16) 0.93 (0.77-1.14) 0.82 (0.67-0.99) 0.80 (0.65-0.99) 0.01 hPDI 1.00 0.95 (0.78-1.14) 0.94 (0.77-1.15) 0.86 (0.70-1.04) 0.84 (0.68-1.03) 0.07 uPDI 1.00 1.14 (0.95-1.39) 1.07 (0.87-1.31) 1.18 (0.97-1.45) 1.17 (0.95-1.45) 0.15 Progression-free Survival PDI 1.00 0.84 (0.70-1.01) 0.94 (0.78-1.14) 0.93 (0.77-1.12) 0.80 (0.65-0.98) 0.10 hPDI 1.00 0.86 (0.72-1.03) 0.83 (0.69-1.01) 0.80 (0.67-0.97) 0.80 (0.66-0.97) 0.03 uPDI 1.00 1.12 (0.94-1.34) 1.11 (0.91-1.34) 1.10 (0.91-1.34) 1.15 (0.94-1.41) 0.23 Citation Format: En Cheng, Fang-Shu Ou, Chao Ma, Alan P. Venook, Heinz-Josef Lenz, Eileen M. O’Reilly, Peter T. Campbell, Chaoyuan Kuang, Bette J. Caan, Kimmie Ng, Jeffrey A. Meyerhardt. Plant-based diet and survival among patients with metastatic colorectal cancer: Findings from CALGB/SWOG 80405 (Alliance) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2200.