Hematologic malignancies following external beam radiation therapy for localized prostate cancer

Ojha, Rohit P. Hematologic malignancies following external beam radiation therapy for localized prostate cancer. Doctor of Public Health (Epidemiology), December 2010, 88 pp., 6 tables, 2 illustrations, references, 96 titles.

The incidence of hematologic malignancies following external beam radiation therapy (EBRT) among prostate cancer patients has received limited attention despite evidence that radiation has a role in leukemogenesis and myelomagenesis. Therefore, we investigated the effect of external beam radiation therapy on acute myeloid leukemia and myeloma incidence among prostate cancer patients. 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 and myeloma incidence following definitive therapy with EBRT alone, brachytherapy alone, or surgery alone compared to no definitive therapy. The cohort yielded 184 incident acute myeloid leukemia cases and 344 incident myeloma cases during 1,064,820 person-years of follow-up after prostate adenocarcinoma diagnosis. Patients treated with EBRT had a higher adjusted relative hazard 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). Patients treated with EBRT, brachytherapy, or surgery did not have increased adjusted relative hazards of developing myeloma when each therapy group was compared to patients who were not treated with definitive therapy (EBRT: HR=0.97, 95% CI: 0.70, 1.35; brachytherapy: HR=0.60, 95% CI: 0.28, 1.33; surgery: HR=1.02, 95% CI: 0.75, 1.39). 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. However, our results indicate that neither EBRT nor brachytherapy increases the relative hazard of myeloma incidence among patients with localized or locally advanced prostate adenocarcinoma. Ultimately, our findings may contribute to the collective evidence regarding the risks and benefits of external beam radiation therapy.