Outcomes of once daily and twice daily accelerated partial breast irradiation regimens in hormone receptor positive breast cancer: a single institution experience
1
Issued Date
2026-12-01
Resource Type
ISSN
14655411
eISSN
1465542X
Scopus ID
2-s2.0-105034413865
Pubmed ID
41731602
Journal Title
Breast Cancer Research
Volume
28
Issue
1
Rights Holder(s)
SCOPUS
Bibliographic Citation
Breast Cancer Research Vol.28 No.1 (2026)
Suggested Citation
Jitwatcharakomol T., Gokun Y., Daniel S.J., Mestres-Villanueva M., Young R.L., Eckstein J.M., Andraos T.Y., Healy E.H., White J.R., Bazan J.G., Kumar P., Cochran E.R., Beyer S.J., Jhawar S.R. Outcomes of once daily and twice daily accelerated partial breast irradiation regimens in hormone receptor positive breast cancer: a single institution experience. Breast Cancer Research Vol.28 No.1 (2026). doi:10.1186/s13058-026-02243-6 Retrieved from: https://repository.li.mahidol.ac.th/handle/123456789/116064
Title
Outcomes of once daily and twice daily accelerated partial breast irradiation regimens in hormone receptor positive breast cancer: a single institution experience
Corresponding Author(s)
Other Contributor(s)
Abstract
Background: Accelerated partial breast irradiation (APBI) has shown non-inferior local control compared to whole breast irradiation, but the optimal external-beam regimen is unclear. This study compares two APBI schedules used at our institution: 38.5 Gy in 10 twice-daily fractions and 28.5 Gy in 5 once-daily fractions delivered every other day. Methods: This retrospective, single-institution study includes post-menopausal women with ductal carcinoma in-situ (DCIS) and early-stage hormone receptor positive invasive breast cancer who underwent lumpectomy followed by APBI and endocrine therapy. Outcomes of interest include ipsilateral breast tumor recurrence (IBTR), disease-free survival (DFS), overall survival (OS), radiation toxicities (graded by CTCAE v5.0), and physician-reported (Harvard scale) cosmetic outcomes. Results: A total of 399 patients were eligible: 142 in the 38.5 Gy group and 257 in the 28.5 Gy group. The median age was 66 years. Most patients had T1 tumors or DCIS (97.4%), were treated with 3D-conformal radiation (99.2%) in the prone position (96.0%), and initiated adjuvant endocrine therapy (86.0%). With a median follow-up of 3.4 years, 3-year IBTR was low and comparable (1% for 38.5 Gy vs. 2% for 28.5 Gy; P = 0.46). Three-year DFS was 99% vs. 98% (P = 0.79) and OS was 99% in both groups (P = 0.53). For acute toxicity, grade 1–2 dermatitis was significantly more common in the 38.5 Gy group (61.7% vs. 28.6%, P < 0.01). For late toxicity at 1-year post-treatment, grade 1–2 skin hyperpigmentation (79.5% vs. 32.4%, P < 0.01) and fibrosis (81.6% vs. 51%, P < 0.01) were significantly more common in the 38.5 Gy group than 28.5 Gy group, respectively. No grade ≥ 3 acute or late toxicities were observed. Cosmetic outcomes were similarly excellent. At 1 year, excellent or good cosmesis was observed in 99% of patients in the 38.5 Gy group and 98% in the 28.5 Gy group (P = 0.15), and at 3 years in 97.3% and 94.1%, respectively (P = 0.83). Conclusions: Both regimens—38.5 Gy in 10 twice-daily fractions and 28.5 Gy in 5 once-daily fractions—delivered using 3D-conformal technique in the prone position yielded excellent 3-year outcomes. Nonetheless, the 28.5 Gy regimen demonstrated a lower incidence of acute and late toxicity and may be preferable in this patient population given its lower skin toxicity and increased convenience. Longer follow-up is warranted to confirm these findings.