IS THERE AN INCREASED RISE OF 2ND PRIMARIES FOLLOWING PROSTATE IRRADIATION

Purpose: To assess the risk of developing a second primary cancer foll owing prostate irradiation compared to the underlying risk in patients with prostate cancer. Methods and Materials: The baseline rate of sec ondary cancers following prostate cancer was obtained from a study of 18,135 patients from the Connecticut Tumor Registry, of whom only 12.5 % received radiotherapy. These patients, with a mean age of 72 and a m ean follow-up of 3.9 years, were compared to a cohort of 543 patients (median age 70) with similar follow-up (median 3.9 years), all of whom were treated with definitive radiotherapy at Fox Chase Cancer Center. The possible association between various covariates (age, dose, palpa tion stage, field size, Gleason score, pretreatment PSA) and the devel opment of a secondary cancer was assessed. Results: 1,053 of 18,135 pa tients (5.8%) in the Connecticut Tumor Registry developed a second pri mary cancer compared with 31 of 543 (5.7%) patients treated with prost ate radiation (p = 0.99). Although this risk increases gradually over time, it is not significantly different, at any time period, between t he two groups of patients. Of the 31 secondary primaries in the irradi ated group, 82% had a history of tobacco and/or alcohol use. Only mela nomas were significantly increased compared to the expected rate in an age-matched population (p <0.001). Five of the 31 secondary cancers o ccurred within the radiation field (four bladder, one colon), four wit hin 3 years and only one occurred 9 years after radiotherapy. No assoc iation was found between age (<70 vs. greater than or equal to 70 and as a continuous variable), dose (<74 vs. greater than or equal to 74 G y), palpation stage (<T2C vs. greater than or equal to T2C), field siz e (prostate vs. pelvic), radiation technique (conventional vs, conform al), Gleason score (2-6 vs. 7-10), or pretreatment PSA (<15 vs. greate r than or equal to 15 and as a continuous variable) and the risk of de veloping a second primary. Although a lower radiation dose las a conti nuous variable) correlated with an increased risk of developing a seco ndary cancer (p = 0.04), this phenomenon is likely due to differences in follow-up time. Conclusion: Up to at least 10 years, there is no in creased risk of developing a second primary cancer following prostate irradiation compared to the baseline rate from prostate cancer itself. This risk is not higher in younger patients with localized disease (< T2C), who often must choose between surgery and radiation. The vast ma jority of secondary cancers occurred outside of the radiation field (8 4%) and/or within 3 years of radiotherapy (97%), suggesting they were not caused by radiation. Most of these patients had lifestyles with pr edisposing risk factors. Patients with prostate cancer manifested a si gnificantly increased risk of developing melanomas, suggesting that th ey may benefit from patient education and skin screening examinations. (C) 1998 Elsevier Science Inc.