Intra-Operative Radiotherapy with Photons - Update of a Single Institution Registry Trial

Intraoperative radiotherapy (IORT) allows early-stage breast cancer patients to complete adjuvant radiation at the time of breast conserving surgery (BCS). In this study, we provide updated outcomes of women treated with IORT in the Bronx, New York.

This is a single-centre, prospective, institutional review-board-approved registry trial of patients treated with IORT using the Intrabeam system. Patients included women aged 45 years and older with estrogen-receptor positive, cT1-2N0 invasive carcinoma or grade 1-2, ductal carcinoma in-situ (DCIS). Exclusion criteria included BRCA mutation, neoadjuvant chemotherapy, or multicentric disease. Patients received a single dose of 20 Gy to the lumpectomy surface with 50kVp x-rays. Those with high-risk pathological features were recommended adjuvant whole breast irradiation (WBI). The primary outcome was locoregional recurrence. Secondary outcomes were overall survival and wound-healing complications.

Between January 2018 and January 2024, 257 women were treated with IORT. The median age was 65.7, and most patients (76.7%) did not identify as white. Nine patients were treated bilaterally, yielding 266 treated lumpectomy cavities. Most tumors were pathologically T1 (n =195, 73.3%), followed by Tis (n =38, 14.2%), then T2 (n =31, 11.6%). Forty-three patients (16.6%) were recommended adjuvant WBI. Median follow-up was 3.7 years, during which there were 7 (2.6%) biopsy-proven ipsilateral breast tumor recurrences. Overall survival was 97.3%, and 10 patients (3.9%) had wound-healing complications.

IORT demonstrated a 97.4% locoregional control rate and spared 83.4% of women from the toxicity of WBI. IORT may serve as a safe alternative for women seeking more personalized treatment.