Dosimetric evaluation of VMAT automated breast treatment plans: Towards the establishment of an institutional plan acceptability criteria

Introduction: To evaluate the clinical suitability of the current facility-based treatment plan protocol in establishing acceptability criteria. Material and methods: Automated Volumetric Arc Therapy (VMAT) treatment plans were retrospectively evaluated for intact breast and chest-wall cancer patients from January 2021 to January 2023. Results: A total of 94 patients were planned and treated using automated contouring and VMAT planning technique. The number of patients planned and treated for intact breast and chest-wall were 41 (43.6%) and 53 (56.4%), respectively. The mean intact breast volumes for optimization (Brst_opt) receiving 95% and 105% of the prescribed doses were 92.80% ± 1.11 and 1.54% ± 1.02, respectively. Their corresponding mean chest-wall volumes for optimization (Chst_opt) were 90.65% ± 3.19 and 2.28% ± 2.99, respectively. For left-sided cases, the mean heart dose received was 4.61 Gy ± 1.76 and 5.18 Gy ± 1.55 for intact breast plans and that for chest-wall plans, respectively. The mean ipsilateral lung volume receiving 20 Gy of the prescribed dose was 12.22% ± 3.86 and 13.19% ± 3.74 for intact breast plans and chest-wall plans, respectively. For the Brst_opt and Chst_opt dose metrics were calculated; the mean homogeneity index (HI) was 0.14 ± 0.03 and 0.15 ± 0.04, mean uniformity index (UI) was 1.09 ± 0.03 and 1.11 ± 0.03, and mean conformity index (CI) were 0.92 ± 0.04 and 0.91 ± 0.04, respectively. Conclusions: The dosimetric evaluation shows a good dose distribution in the target volumes with minimal doses to the organs at risk (OAR). Assessment of the current data affirms the clinical usefulness of the facility-adopted protocol in achieving quality treatment plans for intact breast and chest-wall irradiations. The establishment of plan acceptability criteria will help achieve improved overall treatment outcomes.