Acute myeloid leukemia incidence following radiation therapy for localized or locally advanced prostate adenocarcinoma

Introduction: The effect of radiation therapy on acute myeloid leukemia incidence among prostate cancer patients has not been sufficiently elucidated despite evidence that acute myeloid leukemia is a consequence of therapeutic radiation in other primary malignancies. Therefore, we investigated the effect of definitive therapy with radiation therapy (external beam radiation therapy [EBRT] or brachytherapy) on acute myeloid leukemia incidence in a population-based cohort of patients with localized or locally advanced prostate cancer. Methods: We utilized the Surveillance, Epidemiology, and End Results database to identify a cohort of men (n = 168,612) with newly diagnosed prostate adenocarcinoma between January 1988 and December 2003. Cox proportional hazard regression was used to estimate the hazard ratios (HRs) and corresponding 95% confidence intervals (CIs) of acute myeloid leukemia incidence following definitive therapy with EBRT alone, brachytherapy alone, or surgery alone compared to no definitive therapy (i.e. no EBRT, brachytherapy, or surgery). Results: The cohort yielded 184 acute myeloid leukemia cases during 1,064,820 person-years of follow-up after prostate adenocarcinoma diagnosis. Patients treated with EBRT had a higher adjusted relative risk of developing acute myeloid leukemia than patients treated with brachytherapy or surgery when each therapy group was compared to patients who were not treated with definitive therapy (EBRT: HR = 2.05, 95% CI 1.29, 3.26; brachytherapy: HR = 1.22, 95% CI 0.46, 3.22; surgery: HR = 1.24, 95% CI 0.77, 1.98). Conclusions: Our findings suggest that acute myeloid leukemia incidence is a greater concern for patients treated with EBRT than brachytherapy for localized or locally advanced prostate adenocarcinoma.