Tobacco use and survival among veterans with metastatic prostate cancer.

Abstract

38 Background: Tobacco has been associated with the development of many cancers, but its role in prostate cancer remains unclear. We evaluated the relationship between tobacco use and overall survival among veterans with metastatic prostate cancer, adjusting for clinical and demographic covariates such as age at diagnosis, Body Mass Index (BMI), Prostate-Specific Antigen (PSA), and Charlson Comorbidity Index (CCI). Methods: We conducted a retrospective cohort study of 5,889 veterans with known tobacco use diagnosed with de novo metastatic prostate cancer within the Veterans Health Administration. The primary exposure was tobacco use history (ever vs. never) and baseline characteristics were compared with t-tests or Kruskal-Wallis as appropriate. Survival from time of diagnosis was compared with using the Kaplan-Meier method and Cox proportional hazards models were used to estimate hazard ratios (HRs) for tobacco use, both unadjusted and adjusted for age at diagnosis, BMI, PSA, and CCI. Results: Among 5,889 veterans diagnosed with de novo metastatic prostate cancer, 4,115 were known tobacco users (69.9%). The median age at diagnosis in tobacco-users was 72.5 years vs. 74.7 in non-users (p<0.001). Tobacco use prevalence did not differ significantly by race (White: 69.7%, Black: 70.6%, Other: 63.7%; χ²(2)=2.28, p=0.32). Median BMI was 26.9 in users vs. 27.4 (p<0.001). Median survival was 31.5 months (95% CI 30.2–32.8) in users vs. 35.9 months (95% CI 33.7–38.1) in non-users (log-rank p<0.001). Median PSA was 99.3 ng/dL in users vs. 111.0 (p=0.519). The median CCI was 2 in both groups (p=0.093). In multivariate Cox regression, tobacco use was associated with increased mortality (HR: 1.20; 95% CI: 1.11–1.29; p<0.001). In patients with known race (n=3,886), there were no significant differences in prostate cancer mortality (χ²(2)=1.65, p=0.44) or overall survival (log-rank χ²(2)=1.67, p=0.44). Conclusions: Veterans who used tobacco were diagnosed with metastatic prostate cancer at a younger age and had lower BMI. Although PSA and comorbidities did not differ significantly between ever and never tobacco users, tobacco use was independently associated with worse overall survival after adjusting for clinical covariates. No racial disparities in tobacco use, mortality, or survival were observed. These findings highlight the prognostic value of tobacco-use history and support tobacco cessation strategies into prostate cancer prevention. Baseline characteristics and survival by tobacco use status. Variable Tobacco User (Median) Non-User (Median) p-Value Age at Diagnosis (years) 72.5 74.7 <0.001 BMI 26.9 27.4 <0.001 PSA 99.3 111.0 0.519 CCI 2 2 0.093 Survival Time (months) 31.5 35.9 <0.001