Author: Qiu Tang, Yeqiang Tu, Jiahao Wang, Lu Wang 👨🔬
Affiliation: Women's Hospital School of Medicine Zhejiang University, Hangzhou Women's Hospital 🌍
Purpose: The BT boost regions were previously delineated and optimized during EBRT planning process. The differences of DVH parameters addition (PA), deformable dose summation (DS) with BT boost region optimization (DSRO) and non-optimization (DSRNO) were compared in cumulative dose evaluation of combined radiotherapy for patients with LACC.
Methods: 21 patients with LACC divided into two groups were analyzed. 16 of the patients were treated with intracavitary/interstitial brachytherapy (IC/ISBT) and EBRT which included a nodal boost while 5 were treated with IC/ISBT and EBRT with no nodal boost. The dose summation strategy was performed in two methods of PA and DS. For the first method, EBRT and IC/ISBT fractional dose were directly added using DVH PA. In the second method, the techniques of DSRO and DSRNO were performed for combined radiotherapy. The cumulative D90 of the targets (HRCTV and IRCTV) and D2cc of the OARs (rectum and bladder) were compared between PA and DS.
Results: For the targets in the group with EBRT nodal boost, the differences of D90 were 2.57% and 3.19% for HRCTV and IRCTV between DSRO and PA, while DSRNO had D90 that were 6.44% and 7.68% higher for the HRCTV and IRCTV compared to PA. For the OARs in this group, compared to PA, DSRNO had larger differences of D2cc (5.01% and 6.58%) than DSRO (0.67% and 4.29%) for bladder and rectum, respectively. In the group without EBRT nodal boost, the dosimetric differences of targets and OARs between PA and DS were similar.
Conclusion: The cumulative dose using deformable registration technique through optimized EBRT in the BT boost region is more close to the method of DVH parameters addition. We recommend to delineate and optimize the BT boost region in LACC patients with nodal boost in the EBRT for a more accurate dose assessment.