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Brachytherapy. 2019 Jun 20. pii: S1538-4721(18)30750-5. doi: 10.1016/j.brachy.2019.05.007. [Epub ahead of print]

MRI-based interstitial brachytherapy for vaginal tumors: A multi-institutional study on practice patterns, contouring, and consensus definitions of target volumes.

Author information

1
Department of Radiation Oncology, Sunnybrook Health Sciences Centre, Odette Cancer Centre, Toronto, Ontario, Canada. Electronic address: eric.leung@sunnybrook.ca.
2
Department of Oncology, London Health Sciences Centre, London, Ontario, Canada.
3
Department of Radiation Oncology, BC Cancer, Kelowna, British Columbia, Canada.
4
Radiation Medicine Program, Princess Margaret Cancer Centre, Toronto, Ontario, Canada.
5
Department of Radiation Oncology, McGill University Health Centre, Montreal, Quebec, Canada.
6
Department of Oncology, Cross Cancer Institute, Edmonton, Alberta, Canada.
7
Department of Radiation Oncology, CHU de Québec Université Laval, Québec, Québec, Ontario, Canada.
8
Department of Radiation Oncology, Centre Hospitalier de l'Université de Montréal, Québec, Canada.
9
Department of Radiation Oncology, Nova Scotia Cancer Centre, Halifax, Nova Scotia, Canada.
10
Department of Radiation Oncology, Sunnybrook Health Sciences Centre, Odette Cancer Centre, Toronto, Ontario, Canada.
11
Division of Radiation Oncology, Tom Baker Cancer Centre, Calgary, Alberta, Canada.

Abstract

PURPOSE:

Interstitial brachytherapy (ISBT) can be effective for vaginal tumors due to its ability to deliver conformal treatment with 3D planning. As there is no consensus for 3D vaginal brachytherapy (BT) contouring, the goals of this study are to evaluate the variability in practices and contouring, and to develop consensus concepts on target definitions.

METHODS:

A survey/contouring study was conducted with 16 radiation oncologists from 10 Canadian academic centers. The study included three vaginal ISBT cases. Participants were provided staging, prebrachytherapy (pre-BT), and BT MRIs. Participants responded to a questionnaire and contoured on the provided images. Agreement between contours was analyzed. A meeting was held to develop consensus definitions of targets.

RESULTS:

Median ISBT experience was 3.5 years. All 16 participants regularly contour with MRI, whereas three also plan on MRI. For the three cases, there was variation into how CTVHR and CTVIR was defined. Kappa statistics showed higher agreement with bulky tumors (mean 0.59) as compared with small residual tumors (mean 0.29). For all cases, kappa was highest in pre-BT GTVres as compared with BT GTVres (mean 0.58, 0.46). Consensus concepts to define targets were developed.

CONCLUSIONS:

Variations exist in how ISBT targets are defined for vaginal tumors. Highest contouring variability was seen with small residual at BT. Contouring is more consistent on pre-BT MRI as compared with BT MRI suggesting a needle distortion effect. Consensus CTVHR and CTVIR definitions have been developed and further work is warranted to establish international standards.

KEYWORDS:

Brachytherapy; Consensus; Contouring; MRI; Vagina

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