Abstract 6462: Cigarette smoking reduction and lung cancer risk in the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study

Abstract

Abstract Background. Cigarette smoking is a leading cancer risk factor. In addition to quitting smoking, reducing the number of cigarettes/day may decrease risk of lung cancer compared with continuing to smoke more heavily. However, few cohort studies have longitudinal assessments of cigarette use. Methods. We examined the association of changes in smoking status (trying to quit, not smoking at this time, and still smoking) and changes in cigarettes/day with subsequent incidence of lung cancer in 24,613 Finnish male participants of the Alpha-Tocopherol, Beta-Carotene Cancer Prevention (ATBC) Study, a cancer prevention trial of vitamin supplements that collected serial assessments of cigarette use. At baseline (1985-1988), all participants were current smokers 50-69 years old who smoked 5+ cigarettes/day. During the five-to-eight year intervention period, men were asked at 4-month intervals about changes in their smoking use since their last visit. We obtained individual estimates of the proportion of follow-up time (% of time) in each of the three smoking statuses, the transition probabilities between statuses and intercepts and slopes for the number of cigarettes/day. We then examined associations between changes in smoking and in cigarettes/day and subsequent incidence of lung cancer occurring between the end of the trial (April 30, 1993) and December 31, 2012. Using Cox regression, we modeled lung cancer risk ratios (RRs) and 95% confidence intervals (95%CI) associated with changes in smoking (% of time and number of cigarettes/day) relative to individuals who smoked 20 cigarettes/day across all the study visits. Models were additionally adjusted for age at the end of the trial, ATBC intervention group, education, and age at smoking initiation. Results. Overall, 3013 lung cancers were diagnosed during follow-up. The risk of lung cancer was lower among participants who reduced their smoking intensity by 5 or 10 cigarettes/day [RR=0.80(95%CI:0.71,0.89) and RR=0.64(95%CI:0.51,0.81), respectively]. RRs were further decreased among participants who also smoked at only 50% of study visits [-5 cigarettes/day RR=0.71(95%CI:0.57, 0.90) and -10 cigarettes/day RR=0.46(95%CI:0.44, 0.74)]. Individuals with the lowest risk were those who stopped smoking early at follow-up and continued to not smoke over the intervention period. For example, an individual who began the study smoking 15 cigarettes/day, stop smoking at 4 months and remained not smoking had a RR=0.24(95%CI: 0.11, 0.50). Conclusion: Even in the absence of cessation, smokers may meaningfully lower their lung cancer risk by reducing the number of cigarettes they smoke per day and the proportion of time they smoke. Yet, the lowest risk was observed among smokers who quit completely. Citation Format: Daniela S. Gutiérrez-Torres, Sungduk Kim, Paul Albert, Demetrius Albanes, Stephanie J. Weinstein, Maki Inoue-Choi, Neal D. Freedman. Cigarette smoking reduction and lung cancer risk in the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6462.