The analysis also shows that current smokers made unhealthier lifestyle choices: They exercised less, drank more coffee, and had a higher intake of saturated fat and lower intake of calcium than never or former smokers. Smokers – both former and current – consumed more alcohol, but their body mass index was similar to the BMI of never smokers.
The mortality data showed a "statistically significant difference in overall survival across smoking status," at 5 and 10 years after diagnosis, the authors wrote (JAMA 2011;305:2548-2555).
Among never smokers, 89.7% were alive 5 years after diagnosis and 74.8% at 10 years; among former smokers, survival rates were slightly lower at 86.2% and 68.2%, respectively. Among current smokers they fell to 78.8% and 54.8%, respectively.
Although some studies have suggested that smokers tend to have less PSA testing and may be diagnosed at a more advanced stage, the "differential PSA screening across strata of smoking status was unlikely to fully account for our results," wrote the authors, because the percentage of men who had at least one PSA test before their diagnosis varied little among the three groups.
The authors added that direct effect of smoking on prostate cancer progression "is biologically plausible." They proposed four hypotheses: tumor promotion through carcinogens from tobacco smoke, increased plasma levels of total and free testosterone, epigenetic effects such as aberrant methylation profiles, and "nicotine-induced angiogenesis, capillary growth, and tumor growth and proliferation."
"There are very few factors that are known to increase or decrease risk of progression of prostate cancer. My goal is to find out what’s related to the rate of prostate cancer progression and what men can do to improve their chances of survival with prostate cancer," said Dr. Kenfield.
The authors reported they had nothing to disclose.