SAN DIEGO—Radiotherapy for prostate cancer (PCa) may increase patients’ risk of developing a second cancer, notably lung cancer, researchers reported at the American Urological Association annual meeting.

Amanda Black, PhD, MPH, of the National Cancer Institute in Bethesda, Md., and collaborators analyzed data from 76,685 men aged 55-74 years who were randomized into the Prostate, Lung, Colorectal and Ovarian (PLCO) study from 1993-2001. The mean follow-up was six years.

Of 7,479 men with PCa, 43% underwent radiotherapy, 37% underwent radical prostatectomy, 8% received primary hormone therapy, and 12% received no definitive or other treatment. Patients who received radiotherapy were slightly older than those who did not, but the researchers found no differences in smoking history, comorbidities, body mass index, or educational attainment.

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A total of 570 patients were diagnosed with second cancers. The rate of second cancers was 15.5/1,000 person-years in radiotherapy recipients compared with 11.4/1,000 person-years in those not treated with radiation, a difference that translated into a 25% increased relative risk of second cancers in radiotherapy recipients. Compared with men not treated with radiation, those who were had a 60% increased risk of lung cancer, after adjusting for age, race, education, family history of cancer, smoking, and chronic obstructive pulmonary disease.

According to the investigators, the increased relative risk of any second cancer and lung cancer were greater five or more years after treatment. The study also showed that the relative risk for bladder cancer and colorectal cancer was not significantly increased.

The investigators noted that their study is the first to examine the risk of second cancers following PCa radiotherapy and control for potential confounders.

“The increased risk of lung cancer is intriguing and warrants further investigation given the frequency and fatality of this disease,” the authors concluded in their study abstract.