Comparison between two iodine-125 brachytherapy implant techniques: pre-planning and intra-operative by various dosimetry quality indicators

Abstract

Purpose: To prospectively compare two widely used seed implant techniques: pre-planning and intra-operative planning, based on 1 month post-implant CT-based evaluation.

Methods: We report results of a detailed 1 month post-operative dosimetric evaluation and comparison between 142 consecutive men with prostate adenocarcinoma treated by the pre-planning methodology and 214 men treated with the real-time, intra-operative seed implant method.

Results: Baseline parameters patient's age, Gleason score, clinical stage, and gland volume were similar in both groups (p>0.05). Length of physicist time and operating room team time were more than double in the pre-planned group compared to the intra-operative one (205 vs 100 min). Based on day 30 post-implant CT, for patients treated with the pre-planning method, mean V90, V100 and V150 (percent prostate volume receiving 90, 100 and 150% of the prescribed dose) were 67.5, 58.35 and 21.5%, respectively, while for the intra-operative group they were 97.9, 95.2 and 45%, respectively (p<0.01). Mean D90, expressed as percent of target matched peripheral dose (minimal dose covering 90% of the gland volume) was 53% for the pre-planned group and 114% for the intra-operative group of men (p<0.01). Short-term morbidity was minimal in both groups and did not correlate with the technique employed.

Conclusions: This large-scale comparison of implant adequacy favours real-time intra-operative method. While all dosimetric parameters are significantly better with this method, no increased early morbidity was noted. Longer-term PSA-based clinical outcome should substantiate our contention of the superiority of the intra-operative method when compared to the pre-planning one.