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

Abstract 

Objectives

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

Materials and 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 V₁₀₀ (%) and D₉₀ (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.

Keywords: Prostate cancer, Brachytherapy, Implant technique, PSA kinetics