Abstract
PURPOSE: The objective of this study was retrospectively to compare the efficacy and safety of hypofractionated radiotherapy (HFRT) with a simultaneous integrated boost (SIB) or with a sequential boost (SB) after breast-conserving surgery in patients diagnosed with early breast cancer. METHODS: This study enrolled a total of 343 patients diagnosed with T1-2N0-1 breast cancer who had undergone breast-conserving surgery followed by whole-breast irradiation (WBI) without nodal irradiation, between March 2018 and April 2021. Out of 343 patients, 176 (51.3%) received HFRT-SIB treatment, totaling 15 sessions, while the remaining 167 (48.7%) received HFRT-SB treatment, totaling 18 sessions. Demographic characteristics, skin toxicity, radiation pneumonia, and myelosuppression, were compared in the two groups. Three-year local progression free survival (LPFS) rates were determined using the Kaplan-Meier method and compared using the log-rank test. RESULTS: The median follow-up time was 39.7 months (range 24.3-61.3 months). Toxicities rates did not differ significantly in the HFRT-SIB and HFRT-SB groups, including rates of grade 2 skin toxicity (14.8% vs. 13.8%, p = 0.721), Grade 2 radiation pneumonia (2.8% vs. 3.6%, p = 0.355), grades 1, 2 and 3 myelosuppression (12.5%, 5.7% and 1.1%, respectively, vs. 9.6%, 7.8%, and 1.2%, respectively; p = 0.744). Three-year cumulative LPFS rates were similar in the HFRT-SIB and HFRT-SB groups (99.3% vs. 98.6%, p = 0.52). Regional nodal recurrences were observed in one patient in the HFRT-SIB group (after 27.4 months) and in two patients in the HFRT-SB group (after 29.4 and 56.4 months), and a local recurrence was observed in one patient in the latter group after 36.0 months. One patient in the HFRT-SIB group was diagnosed with distant metastases to bone, and one patient in the HFRT-SB group was diagnosed with distant metastases to the liver. CONCLUSION: Similar efficacy and safety of HFRT-SIB and HFRT-SB after breast-conserving surgery in patients with early-stage (T1-2N0-1) breast cancer. Longer-term follow-up is required to further compare their efficacy.