Cigarette smoking may increase a man's risk for developing and dying from prostate cancer, pooled data from 24 studies involving 21,600 men with the disease indicates.

This study "provides good evidence that prostate cancer is likely a smoking-related tumor," Dr. Michael Huncharek, at Meta-Analysis Research Group in Columbia, South Carolina, wrote in an email to Reuters Health.

Prostate cancer is the most common of all cancers striking U.S. men. Estimates from 2008 show 186,000 new prostate cancer cases and 28,000 deaths, yet the cause remains elusive.

In the American Journal of Public Health, Huncharek and colleagues report results of their "meta-analysis" — a research method that pools findings from numerous studies to better illuminate risks not clearly shown in previous individual studies.

They found "surprisingly consistent evidence," Huncharek said, that both the chance of developing prostate cancer and dying from prostate cancer increases with smoking, even though many of the studies analyzed used crude smoking classifications.

For example, they calculated smoking status as ever versus never rather than by packs smoked per day, or did not define changes in smoking or disease status over time in American, Norwegian, Japanese, Swedish, and British men with prostate cancer.

In eight studies that did provide more in-depth number of cigarettes smoked per day in nearly 8,700 men, Huncharek's team estimates 30 percent greater risk of dying from prostate cancer in the heaviest smokers versus nonsmokers.

They likewise estimate 22 percent greater chance for developing prostate cancer in the heaviest smokers, based on pooled information from four studies of about 2,100 men.

However, Huncharek noted, even these studies do not firmly establish an individual smoker's chance for developing or dying from prostate cancer when compared with their nonsmoking counterparts.

He and colleagues, therefore, call for additional research that quantifies how the number of packs and duration of smoking affects risk for developing the disease and its progression.

SOURCE: American Journal of Public Health, April 2010