Prostate-specific antigen kinetics following external-beam radiotherapy and temporary (Ir-192) or permanent (I-125) brachytherapy for prostate cancer

Background and purposeThe aim of the study was the evaluation of PSA kinetics after different radiotherapy methods.Materials and methodsTwo-hundred and ninety five patients received external-beam radiotherapy (EBRT; 70.2 Gy; n = 135), Ir-192 brachytherapy as a boost to EBRT (HDR-BT; 18 Gy + 50.4 Gy; n = 66) or I-125 brachytherapy (LDR-BT; 145 Gy; n = 94) as monotherapy. “PSA bounce” was defined as a PSA rise of ⩾0.2 ng/ml followed by spontaneous return to prebounce level or lower, biochemical failure as “nadir + 2 ng/ml”.ResultsPatients without biochemical failure reached a lower nadir after brachytherapy (median ⩽0.05 ng/ml after LDR- and HDR-BT without NHT) in comparison to EBRT (0.55 ng/ml without NHT; p < 0.01). Not a single patient without NHT and a nadir <0.1 ng/ml failed biochemically (0% vs. 45% with a nadir ⩾0.1 ng/ml; p < 0.01). PSA bounces were found predominantly in the LDR-BT group (42% vs. 23%/20% after HDR-BT/EBRT; p < 0.01). In a multivariate Cox regression analysis, LDR-BT and HDR-BT were associated with a significantly lower biochemical failure rate in comparison to EBRT.ConclusionsPSA kinetics differ significantly following different radiotherapy methods. A lower nadir and a higher biochemical control rate suggest a higher radiobiological efficiency of brachytherapy in comparison to EBRT (with a dose of 70.2 Gy).