145 - Ultra-Hypofractionated Partial Breast Re-Irradiation for Ipsilateral Breast Cancer Recurrence

Purpose/Objective(s):

A second lumpectomy followed by hyperfractionated partial breast re-irradiation (PBrI) emerged as a viable alternative to salvage mastectomy in select patients with an ipsilateral breast tumor recurrence (IBTR) following breast-conserving therapy for early-stage breast cancer. Ultra-hypofractionated regimens involve fewer fractions and have been shown to be efficacious and well tolerated in select women with newly diagnosed early-stage breast cancer. This study evaluates the IBTR, toxic effects and cosmetic outcomes in patients receiving ultra-hypofractionated PBrI following a second lumpectomy.

Materials/Methods:

Twenty-four consecutively treated female patients who had IBTR following prior BCT, declined salvage mastectomy, and underwent a second lumpectomy followed by ultra-hypofractionated PBrI between 2021 and 2025 were identified from a prospectively maintained, multicenter single-institution database. All patients had previously received whole-breast irradiation (88% conventionally fractionated), and 92% had received a sequential cavity boost (median total dose: 61 Gy). Treatment consisted of 26 Gy in five consecutive daily fractions using volumetric modulates arc therapy; two patients (8%) received a simultaneous integrated boost of 30 Gy. Outcomes assessed included IBTR, distant metastases, survival, physician-graded cosmetic outcome, and acute (<3 months) and chronic (>3 months) toxic effects per CTCAE v4.0. Descriptive statistics were used to summarize patient characteristics, treatment details, and outcomes.

Results:

The median age at recurrence was 70 years (range 61–86), with a median time to recurrence of 16.6 years after initial BCT. At recurrence, 96% of tumors were stage 0 (17%) or I (79%), with a median tumor size of 1.2 cm (range 0.1 – 2); 88% were grade 1 or 2, 92% were ER-positive, 79% PR-positive, all were HER2-negative or HER-2-low, and 45% occurred in a different quadrant from the initial tumor. Two patients (8%) received chemotherapy, and 54% received hormonal therapy. At a median follow-up of 12 months (range 0–44), one patient experienced a second IBTR, managed with a third lumpectomy after declining mastectomy. No distant metastases or deaths were observed. Acute toxicities were all mild (grade 1), including dermatitis (40%), breast edema (13%), breast pain (8%), and fatigue (8%), with no grade =2 acute toxicities. Late toxicities included grade 1/2 breast shrinkage (50%), fibrosis (45%), edema (8%), and telangiectasia (4%), with no breast pain or grade =3 toxicities. Cosmetic outcome was rated excellent or good in 71%, while 14% experienced a decline to poor/fair post-PBrI.

Conclusion:

Ultra-hypofractionated PBrI following a second lumpectomy appears to provide favorable local control and acceptable toxic effects and cosmesis in appropriately selected patients. Larger prospective studies with longer follow-up are needed to validate these findings.