Feasibility and Outcomes of Concomitant Boost in Prone Hypofractionated Whole-Breast Irradiation Using 3D-Conformal Radiotherapy.

Background

Adjuvant radiation after breast-conserving surgery (BCS) reduces recurrence and improves survival in early breast cancer. While hypofractionated whole-breast irradiation (WBI) is standard, use of a concomitant boost (CB) remains limited. We report outcomes using moderately hypofractionated WBI with CB (HFRT-CB) delivered in the prone position with 3D conformal radiation therapy (3D-CRT).

Materials And Methods

Following institutional review board approval, records of patients with early-stage, node-negative invasive breast cancer, or ductal carcinoma in situ treated with BCS and HFRT-CB in prone position were retrospectively reviewed. The whole breast received 40 Gy with a CB 48 Gy to the lumpectomy cavity, delivered in 15 fractions. Outcomes included ipsilateral breast tumor recurrence (IBTR), disease-free survival (DFS), local recurrence-free survival (LRFS), and overall survival (OS). Toxicities were graded using CTCAE v4.0, and physician-reported cosmesis using the Harvard Cosmetic Scale.

Results

A total of 393 patients, with a median age of 60, were treated prone between February 2013 and March 2025. Median follow-up was 39 months. At 3 and 5 years, DFS was 98.5% and 97.6%, and LRFS was 99.6% and 98.8%, respectively. IBTR rates were 0.4% and 1.2%. OS was 97.7% and 94.6%, with a 5-year breast cancer-specific survival of 98.8%. One patient (0.3%) had grade 3 acute toxicity; no grade ≥ 3 late toxicities occurred. Good/excellent cosmesis was reported in 96.2% at 1 year and 88.5% at 3 years.

Conclusion

Prone HFRT-CB with 3D-CRT offers excellent tumor control, minimal toxicity, and favorable cosmesis, supporting its use as a safe and efficient adjuvant option after BCS.