Multisector prostate dosimetric quality: Analysis of a large community database

Abstract Purpose To evaluate multi-institutional prostate brachytherapy dosimetric quality using multisector analysis. Methods and Materials In the database, 4547 patients underwent brachytherapy (3094 for125 I, 1437 for103 Pd, and 16 for131 Cs). The original prostate postimplant dosimetry was reported using the maximum dose covering 90% of the prostate volume ( D90 ) and the percentage of the prostate volume covered by the prescription dose ( V100 ). Retrospectively, the dosimetry of all implants was recalculated after segmenting the prostate into 12 sectors (anterior, left and right lateral and posterior, about the center of gravity, and subdivided lengthwise into three—base, midgland, and apex). The dosimetric quality of each sector and combinations of sectors was compared across radionuclides. Results For each radionuclide, there was no significant difference between monotherapy and boost in terms of V100 or D90 . When classified as excellent ( V100 ≥ 90%), standard ( V100 ≥ 80%), or minimal ( V100 70% of lateral and posterior sectors. When stratified by103 Pd vs.125 I, sector analysis did not result in clinically significant dosimetric differences. Conclusions Coverage of base sectors was inferior to midgland and apical sectors, and coverage of anterior sectors was notably inferior to lateral and posterior sectors. Further critique of brachytherapy planning and intraoperative technique is necessary for brachytherapists to minimize these dosimetric differences.