Analysis of second malignancies after modern radiotherapy versus prostatectomy for localized prostate cancer

PurposeTo clarify the risk of developing second primary cancers (SPCs) after radiotherapy (RT) versus prostatectomy for localized prostate cancer (PCa) in the modern era.MethodsThe RT cohort consisted of 2120 patients matched on a 1:1 basis with surgical patients according to age and follow-up time. RT techniques consisted of conventional or two-dimensional RT (2DRT, 36%), three-dimensional conformal RT and/or intensity modulated RT (3DCRT/IMRT, 29%), brachytherapy (BT, 16%), and a combination of 2DRT and BT (BT boost, 19%).ResultsThe overall SPC risk was not significantly different between the matched-pair (HR 1.14, 95% CI 0.94–1.39), but the risk became significant >5 years or >10 years after RT (HR 1.86, 95% CI 1.36–2.55; HR 4.94, 95% CI 2.18–11.2, respectively). The most significant sites of increased risk were bladder, lymphoproliferative, and sarcoma. Of the different RT techniques, only 2DRT was associated with a significantly higher risk (HR 1.76, 95% CI 1.32–2.35), but not BT boost (HR 0.83, 95% CI 0.50–1.38), 3DCRT/IMRT (HR 0.81, 95% CI 0.55–1.21), or BT (HR 0.53, 95% CI 0.28–1.01).ConclusionsRadiation-related SPC risk varies depending on the RT technique and may be reduced by using BT, BT boost, or 3DCRT/IMRT.