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Brachytherapy. 2015 Mar-Apr;14(2):189-96. doi: 10.1016/j.brachy.2014.08.044. Epub 2014 Oct 7.

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

Author information

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 Oncology, Radiation Medicine Program, Princess Margaret Cancer Centre, Toronto, Ontario, Canada.
3
Department of Radiation Physics, Radiation Medicine Program, Princess Margaret Cancer Centre, Toronto, Ontario, Canada.
4
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. 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.

KEYWORDS:

Cancer; Clinical target volume; Dosimetry; Prostate

PMID:
25301338
DOI:
10.1016/j.brachy.2014.08.044
[Indexed for MEDLINE]

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