Background: Tocopherols and carotenoids are naturally occurring antioxidants found in foods that have been shown to affect cancer incidence and progression in laboratory studies. Both α-tocopherol and β-carotene have been studies in relation to cancer incidence but data examining their associations with cancer survival are sparse.
Methods: We prospectively examined serum α-tocopherol, β-carotene and all cancer survival in the Alpha-Tocopherol, Beta-Carotene Cancer Prevention (ATBC) Study cohort of male smokers enrolled between 1985 and 1988. Fasting serum α-tocopherol and β-carotene were assessed in baseline samples donated prior to cancer diagnosis. As of 2010, there were 10,269 deaths in the cohort of which 6,670 were cancer-related. All cancer survival as well as site-specific cancer survival was examined using the Kaplan-Meier method with deaths from other causes treated as censored events. Follow-up time was calculated from the date of diagnosis to death or censoring date, whichever came first. Cox proportional hazards regression was used to evaluate the association between α-tocopherol and β-carotene and cancer survival. Regression models included age at randomization, body mass index, age at cancer diagnosis, smoking years, and serum total cholesterol.
Results: Higher baseline serum α-tocopherol and β-carotene were significantly associated with improved overall cancer survival in a dose-dependent manner. Compared to the lowest quintile (Q1), the hazards ratio (HR) [95% confidence interval (CI)] for the highest quintile (Q5) of α-tocopherol was 0.81 (0.74, 0.89), Ptrend<0.0001. Similarly, the HR (95% CI) Q5 vs. Q1 for β-carotene was 0.72 (0.67, 0.78), Ptrend<0.0001. When examining specific cancer sites, higher serum α-tocopherol at baseline was associated with improved survival of: colorectal cancer, HR (95% CI) Q5: 0.62 (0.40, 0.97), Ptrend=0.005, and pancreatic cancer, HR (95% CI) Q5: 0.76 (0.51, 1.13), Ptrend=0.07. Higher baseline serum β-carotene was significantly associated with improved survival of: lung cancer, HR (95% CI) Q5: 0.83 (0.74, 0.93), Ptrend=0.0009; stomach cancer, HR (95% CI) Q5: 0.61 (0.38, 0.96), Ptrend=0.01; and, liver cancer HR (95% CI) Q5: 0.53 (0.30, 0.95), Ptrend=0.02. Serum β-carotene was also associated with a marginally significant improvement in survival of prostate cancer (Q5 HR (95% CI) 0.87 (0.66, 1.14), Ptrend=0.05) and bladder cancer (Q5 HR 0.63 (0.38, 1.05), Ptrend=0.03).
Conclusion: Higher circulating concentrations of α-tocopherol and β-carotene are related to improved cancer survival in this cohort of male smokers. These results suggest higher dietary intake of these micronutrients prior to cancer diagnosis may contribute to improved survival. Replication of our findings and mechanistic studies are warranted to shed light on the observed associations.
Citation Format: Kristin A. Moy, Stephanie Weinstein, Satu Männistö, Demetrius Albanes. Serum alpha-tocopherol, beta carotene and cancer survival in the ATBC Study. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2183. doi:10.1158/1538-7445.AM2014-2183