Sector analysis of dosimetry of prostate cancer patients treated with low-dose-rate brachytherapy

PURPOSE: Brachytherapy is an effective single treatment modality for low-and intermediate-risk prostate cancer. Here, we compare the radiation doses in different prostate sectors between the preimplant planning images and the postimplant dosimetry. METHODS AND MATERIALS: Two hundred fifteen consecutive patients treated for prostate cancer by I-125 seed brachytherapy were assessed. Pretreatment plans using transrectal ultrasound images of the prostate were compared with the dose calculated on posttreatment MRI and CT scans obtained 1 month after seed implantation. Twelve sectors were generated by dividing the prostate base, midgland, and apex into four quadrants each. Pretreatment and posttreatment dosimetry were compared between the 12 different sectors of the prostate. RESULTS: Average V-100 (percentage of prostate volume that receives 100% of the prescribed dose) in the preimplant planning images of the prostate was 99.9 +/- 0.25% compared with postimplant V-100 of 94.8 +/- 3.77% (p < 0.0001). Prostate V-100 in the postimplant dosimetry was >91% in all sectors, except the anterior base sector, in which it was 64.87 +/- 20.96%. Average 1-month D-90 (the dose to 90% of the prostate volume) was 114.5 +/- 10.55%. D-90 at 1 month compared with preimplant planning was lower in the prostate base and higher in the prostate apex (p < 0.001). CONCLUSIONS: Our results show that in I-125 seed brachytherapy, prostate base receives a lower dose and apex receives a higher dose compared with preimplant planned dose coverage. (C) 2014 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.