Dosimetric evaluation of clinical target volume in the postimplant analysis of low-dose-rate brachytherapy for prostate cancer - Abstract

PURPOSE: Brachytherapy is an effective single treatment modality for low- and intermediate-risk prostate cancer.

In this study, we defined a clinical target volume (CTV) and evaluated its dosimetry 1 month after the low-dose-rate brachytherapy procedure.

METHODS AND MATERIALS: One hundred ninety-eight consecutive patients treated for prostate cancer by iodine-125 seed brachytherapy were assessed. Prostate dosimetry was stratified according to British Columbia Cancer Agency criteria, with good implants having both V100 (percentage of target volume that receives 100% of the prescribed dose) > 85% and D90 (percentage of the prescribed dose received by 90% of the target volume) > 90%, suboptimal implants with V100 of 75-85%, or D90 80-90%, whereas poor implants were defined as those with V100 < 75 or D90 < 80%. CTV dosimetry stratification was performed according to the same dose coverage criteria, albeit to the CTV.

RESULTS: One hundred ninety-two patients (97%) had good prostate radiation coverage, whereas only 165 patients (83%) had good postimplant CTV dosimetry. Patients with suboptimal vs. good CTV dosimetry had prostate edema of 7.8 ± 0.2% vs. 0.2 ± 0.1%, respectively (p = 0.001).

CONCLUSIONS: Prostate seed implants with optimal dosimetry to prostate may still have suboptimal D90 and V100 for the CTV, especially in the presence of postimplant edema. A consensus is needed for definition and evaluation of CTV in postimplant setting for low-dose-rate prostate brachytherapy.

Written by:
Nasser NJ, Sappiatzer J, Wang Y, Borg J, Saibishkumar EP.   Are you the author?
Department of Radiation Oncology, Radiation Medicine Program, Princess Margaret Cancer Centre, Toronto, Ontario, Canada; Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada; Department of Radiation Physics, Radiation Medicine Program, Princess Margaret Cancer Centre, Toronto, Ontario, Canada.  

Reference: Brachytherapy. 2014 Oct 7. pii: S1538-4721(14)00633-3.
doi: 10.1016/j.brachy.2014.08.044

PubMed Abstract
PMID: 25301338 Prostate Cancer Section