PURPOSE:We report on quality of dose delivery to target and normal tissues from low-dose-rate prostate brachytherapy using postimplantation dosimetric evaluations from a random sample of U.S. patients.
METHODS AND MATERIALS:Nonmetastatic prostate cancer patients treated with external beam radiotherapy or brachytherapy in 2007 were randomly sampled from radiation oncology facilities nationwide. Of 414 prostate cancer cases from 45 institutions, 86 received low-dose-rate brachytherapy. We collected the 30-day postimplantation CT images of these patients and 10 test cases from two other institutions. Scans were downloaded into a treatment planning system and prostate/rectal contours were redrawn. Dosimetric outcomes were reanalyzed and compared with calculated outcomes from treating institutions.
RESULTS: Median prostate volume was 33.4cm3. Reevaluated median V(100), D(90), and V(150) were 91.1% (range, 45.5-99.8%), 101.7% (range, 59.6-145.9%), and 53.9% (range, 15.7-88.4%), respectively. Low gland coverage included 27 patients (39%) with a D90 lower than 100% of the prescription dose (PD), 12 of whom (17% of the entire group) had a D90 lower than 80% of PD. There was no correlation between D90 coverage and prostate volume, number of seeds, or implanted activity. The median V100 for the rectum was 0.3cm3 (range, 0-4.3cm3). No outcome differences were observed according to the institutional strata. Concordance between reported and reevaluated D90values (defined as within ±10%) was observed in 44 of 69 cases.
CONCLUSIONS: Central review of postimplantation CT scans to assess the quality of prostate brachytherapy is feasible. Most patients achieved excellent dosimetric outcomes, yet 17% had less than optimal target coverage by the PD. There was concordance between submitted target-coverage parameters and central dosimetric review in 64% of implants. These findings will require further validation in a larger cohort of patients.
Written by:
Zelefsky MJ, Cohen GN, Bosch WR, Morikawa L, Khalid N, Crozier CL, Lee WR, Zietman A, Owen J, Wilson JF, Devlin PM. Are you the author?
Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, New York, NY.
Reference: Brachytherapy. 2012 Jul 20. Epub ahead of print.
doi: 10.1016/j.brachy.2012.04.001
PubMed Abstract
PMID: 22819388
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