Prospective comparison of PSA kinetics following two different prostate cancer brachytherapy planning methods: preoperative and real-time intraoperative dosimetry planning.

Objective: Preoperative planning (PP) and intraoperative planning (IoP) are established (125)I-brachytherapy techniques for the treatment of localized prostate cancer. We prospectively compared the effects of each method on reducing PSA levels.

Methods: One hundred eighty patients treated with brachytherapy as monotherapy without neoadjuvant androgen deprivation therapy or external beam radiation using PP (75) or IoP (105) methodologies and with ≥ 5 years of follow-up were included in the study. CT-based dosimetry was calculated 1 month postoperatively. PSA was obtained every 3 months for the first year and semiannually thereafter. Available PSA and dosimetric data from both groups were analyzed and compared.

Results: At 5 years after brachytherapy, the probability of having a nadir PSA value < 0.5 ng/ml was 90% in the IoP group compared with 60% in the PP group (P < 0.0001). The rate of PSA decline was 3-fold faster in the IoP group than in the PP group. Dosimetry results highly favored the IoP method: mean V(100) (%) and D(90) (Gy) were 95 and 180 vs. 60 and 81 (P < 0.001), respectively.

Conclusions: Our initial finding of highly superior postimplant CT dosimetry calculations of the IoP method are now substantiated by the biochemical favorable results (PSA kinetics) of this method.