Objectives: this study aimed to evaluate the evolution of planned dose distribution quality in two groups of breast cancer patients treated with hypofractionated intensity-modulated radiotherapy (IMRT) using Helical TomoTherapy® at our institute 5 years apart. Methods: the analysis included two cohorts of patients who underwent implant-based immediate breast reconstruction (IBR) and received post-mastectomy IMRT to the chest wall and infra/supraclavicular lymph nodes, following a 15-fraction regimen (2.67 Gy per fraction). The first group was treated between 2012 and 2015, while the second received treatment between 2019 and 2020. Dosimetric indices derived from dose-volume histograms used in clinical practice were analyzed to assess dose distribution quality. A quantitative scoring system was applied retrospectively to compare the two groups in terms of target coverage and organ-at-risk (OAR) sparing. Additionally, capsular contracture (CC) incidence was examined in both cohorts. Results: A total of 240 patients were included in the study. The percentage of optimal treatment plans increased from 70.8% in the 2012-2015 cohort to 77.5% in the 2019-2020 cohort, while compromised plans decreased from 10.8% to 7.5%. Furthermore, the incidence of moderate-to-severe CC dropped from 54.8% in the earlier cohort to 43.5% in the later one. Conclusions: Helical Tomotherapy® has demonstrated the ability to achieve a high rate of optimal treatment plans concerning both PTV coverage and OAR sparing in a challenging population of postmastectomy patients with IBR. The learning curve showed that, after 5 years, the rate of optimal plans was increased, accompanied by a reduction in compromised plans and treatment-related toxicity.
Keywords: breast cancer; intensity-modulated radiotherapy (IMRT); plan quality; post-mastectomy radiotherapy (PMRT).