Patient's specific integration of OAR doses (D2cc) from EBRT and 3D image-guided brachytherapy for cervical cancer.

Edgar Gelover,Cabel Katherine,Christopher Mart,Wenqing Sun,Yusung Kim

doi:10.1002/acm2.12247

Edgar Gelover, Cabel Katherine + Show 3 more

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https://doi.org/10.1002/acm2.12247

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Abstract

The objective of this study was to assess the recommended DVH parameter (e.g., D2 cc) addition method used for combining EBRT and HDR plans, against a reference dataset generated from an EQD2‐based DVH addition method. A revised DVH parameter addition method using EBRT DVH parameters derived from each patient's plan was proposed and also compared with the reference dataset. Thirty‐one biopsy‐proven cervical cancer patients who received EBRT and HDR brachytherapy were retrospectively analyzed. A parametrial and/or paraaortic EBRT boost were clinically performed on 13 patients. Ten IMRT and 21 3DCRT plans were determined. Two different HDR techniques for each HDR plan were analyzed. Overall D2 cc and D0.1 cc OAR doses in EQD2 were statistically analyzed for three different DVH parameter addition methods: a currently recommended method, a proposed revised method, and a reference DVH addition method. The overall D2 ccEQD 2 values for all rectum, bladder, and sigmoid for a conformal, volume optimization HDR plan generated using the current DVH parameter addition method were significantly underestimated on average −5 to −8% when compared to the values obtained from the reference DVH addition technique (P < 0.01). The revised DVH parameter addition method did not present statistical differences with the reference technique (P > 0.099). When PM boosts were considered, there was an even greater average underestimation of −8~−10% for overall OAR doses of conformal HDR plans when using the current DVH parameter addition technique as compared to the revised DVH parameter addition. No statistically significant differences were found between the 3DCRT and IMRT techniques (P > 0.3148). It is recommended that the overall D2 cc EBRT doses are obtained from each patient's EBRT plan.

Highlights

Integration of concomitant chemotherapy, external beam radiotherapy (EBRT), and intracavitary brachytherapy (BT) is the standard of care in the curative management of locally advanced cervical cancer.[1]
We present a practical revised DVH parameter addition method where the volumetric OAR parameters (e.g., D2 cc) are obtained from each patient’s EBRT plan, instead of assuming a completely uniform EBRT prescription dose
The overall D2ccEQD2 parameters for the rectum, bladder, and sigmoid that were obtained from a revised DVH parameter addition technique presented no statistical differences (P > 0.0981) with the reference dataset values regardless of conformal, volume optimization, and Point A HDR plans

Summary

Introduction

Integration of concomitant chemotherapy, external beam radiotherapy (EBRT), and intracavitary brachytherapy (BT) is the standard of care in the curative management of locally advanced cervical cancer.[1] Using a BT boost is linked with improved pelvic control[2] and overall survival.[2,3] The first use of BT for the treatment of cervical cancer dates back to 1903.4 The use of three-dimensional (3D) imaging techniques, such as computerized tomography (CT) and magnetic resonance imaging (MRI), have been rapidly replacing planar x-ray imaging in BT treatment planning This follows the recommendations of the Groupe Europeen de Curietherapie-European Society for Therapeutic Radiology and Oncology (GEC-ESTRO),[5,6,7] the American Brachytherapy Society (ABS),[8,9] EMBRACE (An intErnational study on MRI-guided BRachytherapy in locally Advanced CErvical cancer) protocol,[10] and a recent International Commission on Radiation Units and Measurements (ICRU) Report #89.11 Volumetric dose parameters for targets and organs-at-risk (OARs) were introduced and used, allowing clinicians to customize isodose lines with the goal of achieving maximal coverage of the high-risk clinical target volume (HR-CTV) while irradiating OARs as little as possible. The adopted EMBRACE protocol phrase for this is “DVH parameter addition”.10 In this DVH parameter addition technique, the EBRT component dose distributions (at least for the volumetric OAR parameters (D2 cc and D0.1 cc)), are assumed to be completely uniform EBRT prescription doses following the recommendations of the EMBRACE protocol.[5,7,10]

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