PSA kinetics after external beam radiotherapy alone or combined with an iridium brachytherapy boost to deliver 85 grays to prostatic adenocarcinoma.

Purpose: Increasing the dose to prostatic adenocarcinoma in conformal external beam therapy (EBT) has resulted in increased levels of PSA normalization and increased percentage of biochemical disease-free survival rates. However technical problems due to prostate motion inside the pelvis or patients' set-up make difficult the realization of the EBT boost fields above 72 Gy. Brachytherapy which overcomes these problems was investigated to deliver the boost dose to achieve 85 Gy. PSA nadir which has been identified as the strongest independent predictor of any failure in many studies has been used as the end point for early evaluation of this work.
Patients and Methods: In a retrospective way we report on 163 patients' PSA kinetics after EBT alone to 68 Gy or EBT first and a brachytherapy boost up to 75 or 85 Gy.
Results: At 12 months follow-up, PSA nadirs percentage < or = 0.5 or < or = 1 ng/ml increased from 7.5 and 20.7% after 68 Gy EBT to 49.8 and 71.2% after a brachytherapy boost to deliver 85 Gy (p < 0.0001). In the Cox PH model analysis, the total dose remained the most important factor for predicting PSA normalization.
Conclusions: These results are in accordance with the most recent results published after conformal EBT at the same 80 Gy level of dose. If confirmed on a higher number of patients they could place brachytherapy among the most accurate methods of boosting in the radiation treatment of prostatic carcinoma.