Planning System-dependent Recommendations of Intensity-modulated Technique for Breast Radiotherapy: A Literature Review-based Adaptation and Institutional Dosimetric Experience from a Large-volume Tertiary Cancer Care Hospital

This article aims to identify, through a literature review, the best intensity-modulated technique (IMRT)/volumetric-modulated arc therapy (VMAT) for the breast/chest wall (Br/CW) as a function of the treatment planning system (TPS) and present the institutional dosimetric data for the same. A PubMed search was conducted following intensity-modulated irradiation techniques (IMRT) presented in the study: field-in-field (FiF), tangential IMRT (t-IMRT), multi-field IMRT, tangential VMAT (t-VMAT), half-arc VMAT (HA-VMAT), and large arc VMAT (LA-VMAT). The literature with at least one arm VMAT is included in this study. A total of 370 articles were identified between 2010 and 2022, out of which 19 articles were found to be unique. These articles were classified in terms of the TPS used: Eclipse (9), Monaco (6), RayStation (2), Pinnacle (1), and one unidentified TPS. Based on the literature review, dosimetric attributes, and second cancer risk analysis (SCRA), t-IMRT was found to be the most preferable technique in Eclipse, Pinnacle, and RayStation TPS. However, for Monaco TPS, t-VMAT (approximately 30 degrees tangential arc) offers better dose coverage with lower organ-at-risk (OAR) doses. In terms of OAR doses and SCRA, LA-VMAT (>= 210 degrees) and HA-VMAT (180 degrees) are avoidable techniques in any TPS, and FiF should be preferred over these two techniques. In our present institution, which uses the Eclipse TPS, data for 300 patients treated with t-IMRT were collected. The data included beam angle, monitor unit [MU], target coverage (D95% and V105% [cc]), and analysis of the maximum (%), and mean dose (%) of the OAR. t-IMRT utilizes two medial and three lateral tangential beams placed at a spread of approximately 10 degrees and 20 degrees, respectively. The results showed a D95% of 96.3 +/- 1.2% and a V105% of 4.9 +/- 7.0 cc. The mean doses to the heart and ipsilateral lung were 10.1 +/- 20.9% and 11.4 +/- 10.2%, respectively. The mean MU was 1282.7 +/- 453.4. Based on the findings, the most preferred intensity-modulated technique for Eclipse, Pinnacle, and RayStation is t-IMRT, while for Monaco, it is t-VMAT. The data from the Eclipse planning system demonstrate a satisfactory dosimetric outcome for t-IMRT. However, the use of VMAT techniques employing an arc angle between 180 degrees and 210 degrees or higher is strongly discouraged.