Possibilities and limitations of left breast IMRT techniques in practice IMRT S&S versus VMAT

Abstract

Author(s): Rachid Errifai*, Siham Bouaouad and B.K. El gueddari

Introduction: The purpose of this manuscript is to compare dosimetry differences based on two types of radiotherapy plans for postoperative left breast cancer. In particular, based on a clinical dosimetric study, intensitymodulated radiation therapy (IMRT) and volumetric-modulated Arc Therapy (VMAT) plans were implemented in 10 cases of postoperative left breast cancer patients and nodes.

Material and Methods: In our study, the prescribed dose was 50 Gy to the target volume delivered in 25 fractions of 2 Gy. The dose objectives at the PTV (Planning Target Volume) and the OAR (Organs at Risk) are detailed in Table 1. The main objective was to respect a good coverage of the target volume (PTV). For the contralateral lung, contralateral breast, and heart, the objective was to achieve the lowest possible dose.

Results: For target volume coverage (PTV): Table 1 and Table 1 show that all the dosimetric criteria are met regardless of the technique. The PTV volume receiving at least 95% of the prescribed dose is lower than 95% with a major contribution of the VMAT technique compared to the S&S IMRT technique of 2.6%. The maximum dose received by the PTV is lower in VMAT than in S&S IMRT by 0.4%. For the SROs: the result is similar in both techniques, however a decrease of 1.7% of the dose received by the homolateral lung receiving at least 20 Gy is noted in favor of the S&S IMRT technique (Table 2). The dose to the heart is generally higher with VMAT, with a maximum difference of 22.2% for the heart volume receiving at least 10 Gy. Regarding treatment time, it is reduced from 11 min with S&S IMRT to 2 min with VMAT.

Conclusions: We have shown that for the treatment of breast cancer, the VMAT technique offers better dose conformation at the PTV and lower peak doses compared to S&S IMRT, For the homolateral lung, contralateral breast, and healthy tissues, VMAT allows a decrease of the doses received compared to IMRT S&S but this is accompanied by an increase of the dose received by the heart for the volume of the heart receiving at least 10 Gy, this is also accompanied by a very significant reduction of the treatment time in favor of the VMAT technique.

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