Second malignancies in prostate carcinoma patients after radiotherapy compared with surgery

BACKGROUND. In the treatment of prostate carcinoma, radiotherapy and surger y are common choices of comparable efficacy; thus a realistic comparison of the potential long term sequelae, such as the risk of second malignancy, m ay be of relevance to treatment choice. METHODS. Data regarding the rate of incidence from the Surveillance, Epidem iology, and End Results Program cancer registry (1973-1993) were used to co mpare directly second malignancy risks in 51,584 men with prostate carcinom a who received radiotherapy (3549 of wham developed second malignancies) wi th 70,539 men who underwent surgery without radiotherapy (5055 of whom deve loped second malignancies). Data were stratified by latency period, age at diagnosis, and site of the second malignancy. Directly comparing the risks in the radiotherapy group with those in the surgery group largely avoids pr oblems associated with underreporting second malignancies. RESULTS. Radiotherapy for prostate carcinoma was associated with a small, s tatistically significant increase in the risk of solid tumors (6%; P = 0.02 ) relative to treatment with surgery. Among patients who survived for great er than or equal to 5 years, the increased relative risk reached 15%, and w as 34% for patients surviving greater than or equal to 10 years. The most s ignificant contributors to the increased risk in the irradiated group were carcinomas of the bladder, rectum, and lung, and sarcomas within the treatm ent field. No significant increase in rates of leukemia was noted. CONCLUSIONS. Radiotherapy for prostate carcinoma was associated with a stat istically significant, although fairly small, enhancement in the risk of se cond solid tumors, particularly for long term survivors. The pattern of exc ess second malignancies among men treated with radiotherapy was consistent with radiobiologic principles in terms of site,dose, and latency. In absolu te terms, the estimated risk of developing a radiation-associated second ma lignancy was 1 in 290 far all prostate carcinoma patients treated with radi otherapy, increasing to 1 in 70 for long term survivors (greater than or eq ual to 10 years). Improvements in radiotherapeutic techniques, along with d iagnosis at younger ages and earlier stages, are resulting in longer surviv al times for patients with prostate carcinoma. Because of the long latency period for radiation-induced tumors, this may result in radiation-related s econd malignancy risk becoming a more significant issue. (C) 2000 American Cancer Society.