Cigarette smoking during external beam radiation therapy for prostate cancer is associated with an increased risk of prostate cancer-specific mortality and treatment-related toxicity.

Objective: To evaluate whether a history of smoking or smoking during therapy after external beam radiotherapy (EBRT) for clinically localised prostate cancer is associated with increased treatment-related toxicity or disease progression.

Patients And Methods: Of 2358 patients receiving EBRT for prostate cancer between 1988 and 2005, 2156 had chart-recorded smoking histories. Patients were classified as 'never smokers', 'current smokers', 'former smokers', and 'current smoking unknown'. Variables considered included quantity of tobacco use in pack-years, duration of smoking, and, for former smokers, how long before initiation of RT the patient quit smoking, when available. The median EBRT dose was 8100 Gy and the median follow-up was 95 months. Toxicity was graded according to the National Cancer Institute's Common Terminology Criteria for Adverse Events.

Results: Current smoking significantly increased the risks of both prostate-specific antigen relapse [hazard ratio (HR) 1.4, P = 0.02] and distant metastases (HR 2.37, P < 0.001), as well as prostate cancer-specific death (HR 2.25, P < 0.001). Multivariate analysis showed that smoking was also associated with increased risk of EBRT-related genitourinary toxicities (current smoker, HR 1.8, P = 0.02; former smoker, HR 1.45, P = 0.01). Smoking did not increase gastrointestinal toxicity.

Conclusions: Current smokers with prostate cancer are at increased risk of biochemical recurrence, distant metastasis, and prostate cancer-related mortality after definitive RT to the prostate. Current and former smokers, regardless of duration and quantity of exposure, are at an increased risk of long-term genitourinary toxicity after EBRT. Oncologists should encourage patients to participate in smoking-cessation programmes before therapy to potentially lower their risk of relapsing disease and post-treatment toxicities.