Five-Year Results from a Single Institution Utilizing IORT for Early-Stage Breast Cancer in a Population Comprised of a Majority of African American Women

Abstract

Intraoperative radiotherapy (IORT) for early-stage hormone receptor (HR) positive, HER2neu non-amplified breast cancer has demonstrated non-inferior rates of local control at 5 years compared with external beam radiotherapy (EBRT) based on the phase III TARGIT-A trial published in 2014. We present our 5-year institutional experience utilizing IORT since the TARGIT-A publication treating a cohort comprised primarily of African American (AA) patients, an important population whose experience with IORT is not currently well defined.Data from women with early-stage HR positive, HER2neu non-amplified breast cancer who underwent lumpectomy and immediate or delayed IORT (20 Gy prescribed to cavity surface) between 2015 and 2020 were collected on an IRB-approved study. Retrospective review of clinicodemographic variables, including age, race, body mass index (BMI), tumor pathology, and dosimetry was performed. Primary endpoints included postoperative complications, adjuvant therapies, and local recurrence rates. Statistical analyses were performed using χ2 and Student's t-tests to identify associations between categorical and continuous variables.257 patients (168 AA, 81 Caucasian, 8 other) were analyzed. Most were clinical stage IA (n = 195, 75.6%) with invasive ductal carcinoma (n = 141, 60.5%). Median age at time of IORT was 68 years (46 - 99). On average, AA women had a significantly higher BMI (32.4 vs. 28.9 kg/m2, P = 0.003) and pathologic tumor size (1.69 vs. 1.25 cm, P = 0.003) compared to Caucasian women. Caucasian women were more likely to experience a postoperative wound complication (13.6% vs. 6.0%, P = 0.04). There was one Grade 3 complication related to a surgical site infection requiring hospitalization. Max point dose to skin was not found to correlate with developing a wound complication (4.09 Gy vs. 4.06 Gy, P = 0.46). At a median follow up of 21 months there were 10 ipsilateral recurrences (3.9%, all in index quadrant) without a significant difference in frequency in IBTR between AA and Caucasian women (n = 4, 4.4% vs. n = 3.7%, P = 0.39). One patient had < 1mm DCIS margins who did not receive EBRT & two declined endocrine therapy, one of which had a focally positive margin at surgery. There were no significant differences in number of patients receiving adjuvant chemotherapy or EBRT between AA and Caucasian women (n = 24, 14.3% vs. n = 11, 13.6% P = 0.88). There was one death from metastatic breast cancer in an AA patient who declined adjuvant therapy for high-risk disease.This institutional cohort comprised predominantly of AA women showed acceptable rates of local control and no difference in IBTR rates between races. Postoperative complication rates were low (n = 21, 8.1%) with only one severe toxicity observed. Future work will examine additional clinicopathologic features and dosimetric data to assess their association with the risk of IBTR and postoperative complications.