Nicola J Nasser1, Yinkun Wang2, Jette Borg2, Elantholi P Saibishkumar3. 1. Department of Radiation Oncology, Radiation Medicine Program, Princess Margaret Cancer Centre, Toronto, Ontario, Canada; Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada. 2. Department of Radiation Physics, Princess Margaret Cancer Centre, Toronto, Ontario, Canada. 3. Department of Radiation Oncology, Radiation Medicine Program, Princess Margaret Cancer Centre, Toronto, Ontario, Canada; Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada. Electronic address: saibish.elantholi@rmp.uhn.on.ca.
Abstract
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 (125)I 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 V100 (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 V100 of 94.8 ± 3.77% (p < 0.0001). Prostate V100 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 D90 (the dose to 90% of the prostate volume) was 114.5 ± 10.55%. D90 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 (125)I seed brachytherapy, prostate base receives a lower dose and apex receives a higher dose compared with preimplant planned dose coverage.
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 (125)I 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 V100 (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 V100 of 94.8 ± 3.77% (p < 0.0001). Prostate V100 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 D90 (the dose to 90% of the prostate volume) was 114.5 ± 10.55%. D90 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 (125)I seed brachytherapy, prostate base receives a lower dose and apex receives a higher dose compared with preimplant planned dose coverage.
Authors: Michelle I Echevarria; Arash O Naghavi; Puja S Venkat; Yazan A Abuodeh; Carlos Chevere; Kosj Yamoah Journal: J Contemp Brachytherapy Date: 2016-11-02