A study that tracked tens of thousands of midlife and older men for more than 20 years has found that vigorous exercise and other healthy lifestyle habits may reduce their chances of developing a lethal type of prostate cancer by up to 68%. The study was published in the Journal of the National Cancer Institute (doi:10.1093/jnci/djv329).

Most prostate cancers are clinically indolent, meaning they do not metastasize and are nonlife-threatening; however, a minority of patients have aggressive disease that invades the bone and other organs, and is ultimately fatal. Lead author Stacey Kenfield, ScD, of University of California San Francisco (UCSF), and a team of researchers at UCSF and Harvard University in Boston, Massachusetts, focused on this variant of prostate cancer to determine if exercise, diet, and smoke-free status might have life-saving benefits.

In the study, the researchers analyzed data from two US studies: the Health Professionals Follow-Up Study that tracked more than 42 000 males age 40 to 75 years, from 1986 to 2010; and the Physicians’ Health Study that followed more than 20 000 males age 40 to 84 years, from 1982 to 2010.

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To gage the effects of lifestyle habits, the researchers developed a score based on the results of the Health Professionals survey, then applied it to the Physicians’ study. They assigned 1 point for each affirmative response to questions about regular intense exercise that induced sweating, body mass index (BMI) under 30, tobacco-free status for a minimum of 10 years, high intake of fatty fish, high intake of tomatoes, and low intake of processed meat.

To reduce error, participants had to be free of diagnosed cancer at the start of the study and a 4-year lag was imposed to rule out those who unknowingly had lethal prostate cancer, which was determined by evidence of prostate cancer death or metastasis to the bones or other organs, excluding the lymph nodes. Cases were confirmed through medical records and pathology reports, and cause of death was determined by death certificate and medical record, and secondarily by next of kin.

The researchers identified 576 cases of lethal prostate cancer in the Health Professionals’ group and 337 cases in the Physicians’ group. Risk of developing lethal prostate cancer among participants with 5 to 6 points was 68% lower for those in the Health Professionals’ group and 38% lower for those in the Physicians’ group. Among men with 3 points for dietary factors alone, chance of developing lethal prostate cancer was 46% lower in the Health Professionals’ group  and 30% lower for those in the Physicians’ group, vs. those with 0 points in each respective group.

Although there were fewer cases and less detailed data collected in the Physicians’ study, the score was similar in both populations, indicating the potential benefit of healthy lifestyle habits in warding off lethal prostate cancer, said the authors.

“We estimated that 47% of lethal prostate cancer cases would be prevented in the United States if men over 60 [years] had 5 or more of these healthy habits,” said Kenfield, assistant professor in the Department of Urology at UCSF Medical Center, and formerly of the Department of Medicine at Harvard Medical School in Boston, where the study was initiated.

The researchers also calculated that lethal prostate cancer among American men older than 60 years would be reduced by 15% if they consumed at least 7 servings of tomatoes per week and that 17% would be spared this diagnosis if they consumed at least 1 serving of fatty fish per week. Reducing intake of processed meats would cut the risk by 12%, they reported.