Effects of Smoking, Alcohol, and Exercise on Prostate Cancer

Risk of Developing Prostate Cancer

Multiple studies, both case-control and cohort in design, have attempted to examine the effect of smoking on developing prostate cancer. However, the data from these studies are conflicting, with some showing an increased risk while others showing no change in the risk of prostate cancer.

The majority of cohort studies were unable to identify an increased risk of prostate cancer among smokers. These studies included large population-based cohorts from multiple ethnicities and countries, including Korea, the United States, Europe, and Singapore. Only one cohort study conducted in Finland showed a slight increase in the incidence of prostate cancer among smokers. One study even showed an inverse relationship of smoking with prostate cancer in Japanese men.

Several recently performed case control series also showed mixed results. Plaskon et al. showed in a study using the Seattle-Puget Sound Cancer Registry that current smokers had an increased risk of prostate cancer, with an odds ratio of 1.4. They also found a dose–response relationship between number of pack-years smoked and prostate cancer risk. Another study in the United States showed an increased risk of prostate cancer in heavy smoking African-American men, with an odds ratio of 2.57. Contrary to these results, Darlington et al. were unable to show an effect in their case control study from Ontario.

Huncharek et al. performed a meta-analysis on 24 cohort studies, which included over 21,000 prostate cancer case participants. In their pooled data, they found no increased risk of prostate cancer in current smokers. However, when the studies contained data where participants were stratified by amount smoked, there was an increased risk of prostate cancer among the highest smokers, although the increase was small, with an RR = 1.11. In this same study, former smokers also had a very slight increase in the incidence of prostate cancer with a RR of 1.09. It appears from the mentioned studies that the overall risk of prostate cancer is increased only slightly, if at all, from cigarette smoking.

Risk of Developing Advanced/Fatal Prostate Cancer

While the data relating to the incidence of prostate cancer is mixed, there is more consistent data that smoking increases the risk of developing advanced or fatal prostate cancer.

Several studies attempted to examine the risk of developing advanced or high-grade cancer in smokers or former smokers. In their cohort study of Japanese men, Sawada et al. examined the effect of smoking on the development of advanced cancers that were detected secondary to symptoms. They were able to show that, while smoking was inversely associated with incident prostate cancer, it tended to increase the risk of developing advanced prostate cancer. Similarly, Murphy et al. attempted to study the effect of smoking on high-grade cancers in a case control study consisting of patients in urology clinics in two major US cities. They showed that in African-American men, who made up a large percentage of the cases and controls, heavy smoking increased the risk of developing high-grade cancer when compared to never or light smokers, with an odds ratio of 1.89.

In a large cohort study conducted on 26,810 men in Maryland, Rohrmann et al. showed that current smokers of 20 or more cigarettes per day and former smokers had a greater risk of death from prostate cancer, with relative risks of 2.38 and 2.75, respectively. Similarly, another large cohort study conducted on American men showed that current smokers were 1.7 times more likely to develop fatal prostate cancer, even though they were not more likely to develop prostate cancer overall. This increased risk of fatal cancer was not identified in former smokers in the same study. In their large meta-analysis, Huncharek et al. also found that current smokers had an increased risk of fatal prostate cancer, and also showed that the heaviest smokers had a 24–30% greater risk of death from prostate cancer than did nonsmokers. Similarly, Rohrmann et al. showed in a separate study of over 145,000 European men, the heaviest smokers (25+ cigarettes per day) or those who had smoked for an extended period of time (40 plus years) had a higher risk of prostate cancer death, with a relative risk of 1.81 and 1.38, respectively, both of which were statistically significant. In their review of the current literature, Zu and Giovannucci go so far as to conclude that the majority of prospective studies showed that current smoking is associated with an increase of 30% in fatal prostate cancer risk when compared to never/nonsmokers.

Summary

The data from several cohort and case-control studies is mixed in regard to smoking leading to an increased risk of prostate cancer. However, several studies did show that current and former smokers were more likely to develop fatal or advanced prostate cancer and these data appear to be more consistent across multiple studies. While the data are not definitive on the effect of smoking, all physicians can surely encourage their patients to discontinue smoking owing to the myriad of health benefits from smoking cessation.