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Brachytherapy. 2017 Nov - Dec;16(6):1184-1191. doi: 10.1016/j.brachy.2017.05.011. Epub 2017 Sep 1.

Total reference air kerma can accurately predict isodose surface volumes in cervix cancer brachytherapy. A multicenter study.

Author information

1
Department of Radiotherapy, Medical University of Vienna, Vienna Austria. Electronic address: karensavannah@gmail.com.
2
Department of Oncology, Aarhus University Hospital Aarhus, Denmark.
3
Department of Radiation Oncology, Gustave Roussy, University Paris-Saclay, Villejuif, France.
4
Department of Radiation Oncology, University Medical Centre Utrecht, The Netherlands.
5
Department of Radiation Oncology, Tata Memorial Hospital, Mumbai, India.
6
Department of Radiotherapy, Medical University of Vienna, Vienna Austria.

Abstract

PURPOSE:

To demonstrate that V60 Gy, V75 Gy, and V85 Gy isodose surface volumes can be accurately estimated from total reference air kerma (TRAK) in cervix cancer MRI-guided brachytherapy (BT).

METHODS AND MATERIALS:

60 Gy, 75 Gy, and 85 Gy isodose surface volumes levels were obtained from treatment planning systems (VTPS) for 239 EMBRACE study patients from five institutions treated with various dose rates, fractionation schedules and applicators. An equation for estimating VTPS from TRAK was derived. Furthermore, a surrogate Point A dose (Point A*) was proposed and tested for correlation with V75 Gy.

RESULTS:

Predicted volumes Vpred = 4965 (TRAK/dref) 3/2 + 170 (TRAK/dref) - 1.5 gave the best fit to VTPS. The difference between VTPS and predicted volumes was 0.0% ± 2.3%. All volumes were predicted within 10%. The prediction was valid for (1) high-dose rate and pulsed dose rate, (2) intracavitary vs. intracavitary/interstitial applicators, and (3) tandem-ring, tandem-ovoid, and mold. Point A* = 14 TRAK was converted to total EQD2 and showed high correlation with V75 Gy.

CONCLUSIONS:

TRAK derived Isodose surface volumes may become a tool for assessment of treatment intensity. Furthermore, surrogate Point A doses can be applied for both intracavitary and intracavitary/interstitial BT and can be used to compare treatments across fractionation schedules.

KEYWORDS:

Cervical cancer; Image-guided brachytherapy; TRAK; Treatment volumes

PMID:
28867617
DOI:
10.1016/j.brachy.2017.05.011
[Indexed for MEDLINE]

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