A prospective phase II trial of 10-fraction whole-breast radiotherapy following breast-conserving surgery

Background:Moderate hypofractionation is established as the standard of care for adjuvant wholebreast radiotherapy after breast-conserving surgery.Ultra-hypofractionated regimens further shorten treatment but have raised concerns about toxicity and cosmetic outcomes.In younger Asian patients frequently requiring a boost, we evaluated a 10fraction whole-breast radiotherapy schedule as a practical and tolerable choice. Methods:This single-arm, prospective phase II trial enrolled 64 patients with early-stage breast cancer at Peking University Cancer Hospital between November 2023 and March 2025.All patients received intensity-modulated radiotherapy (IMRT) with a prescribed dose of 37 Gy in 10 fractions, followed by a sequential tumor-bed boost of 7.4 Gy in 2 fractions according to clinical indications.The primary endpoint was the incidence of grade 2 acute radiation dermatitis; secondary endpoints included patient-reported outcomes, cosmetic assessment, oncologic outcomes and exploratory immune profiling.Clinical Trial registration: ChiCTR2300075391. Results:All patients completed radiotherapy without interruption.Tumor-bed boost was delivered to 58 patients (90.6%).Grade 2 acute dermatitis was observed in 17.2% of patients, with no grade 3 events, and all reactions resolved to grade 0-1 within three months.Among the 11 cases with grade 2 dermatitis, the most frequently affected site was the nipple-areola complex (6 cases, 54.5%).Patient-reported cosmetic and breast symptom scores transiently worsened at two weeks after radiotherapy but recovered thereafter.No significant decline occurred in functional or global quality-oflife domains.Exploratory analyses suggested that prior chemotherapy and lower baseline CD4 T-cell counts were associated with a higher risk of grade 2 dermatitis. Conclusion:This 10-fraction whole-breast radiotherapy regimen was acceptable.These findings support this regimen as a practical alternative for adjuvant breast radiotherapy.