Risk for developing myelodysplastic syndromes in prostate cancer patients definitively treated with radiation.

Background: Exposure to ionizing radiation has been linked to myelodysplastic syndromes (MDS); it is not clear whether therapeutic radiation doses used for prostate cancer pose an increased MDS risk.
Methods: We performed a retrospective cohort study of prostate cancer patients diagnosed between 1986 and 2011 at Cleveland Clinic, comparing those who underwent definitive treatment with radical prostatectomy (RP) to radiotherapy either external beam radiotherapy (EBRT) or prostate interstitial brachytherapy (PI) and to population-based registries. Competing risk regression analyses were used to determine the cumulative risk of developing MDS. All statistical tests were two-sided.
Results: Of 10924 patients, 5119 (47%) received radiation (n = 2183 [43%] in EBRT group and n = 2936 [57%] in PI group) and 5805 (53%) were treated with RP. Overall, 31 cases of MDS were observed, with age-adjusted incidence rates no higher than in population-based registries. In univariate analyses, advancing age (hazard ratio [HR] = 1.14; 95% confidence interval [CI] = 1.09 to 1.20; P < .001) and radiotherapy exposure (HR = 3.44; 95% CI = 1.41 to 8.37; P = .007) were statistically significantly associated with development of MDS. In multivariable analyses, although advanced age (HR = 1.13; 95% CI = 1.06 to 1.19; P < .001) remained statistically associated with MDS, radiation did not, although a small non-statistically significant trend existed for PI-treated patients. MDS rates were no higher than in population-based registries.
Conclusions: With relatively short follow-up, prostate cancer patients definitively treated with radiation did not appear to have a statistically increased risk of subsequent MDS.