Postoperative Seroma Formation Following Intraoperative Electronic Brachytherapy For Early-Stage Breast Cancer

Two prospective randomized trials, TARGIT-A and ELIOT have shown intraoperative radiation (IORT) to be safe and well-tolerated in low risk patients. There is, however, very little data on the rates of seroma formation in patients treated with IORT using electronic brachytherapy. From 12/9/2011 to 4/11/2018, a total of 100 patients (101 treatments) were treated at our institution with partial mastectomy and intraoperative electronic brachytherapy. A balloon applicator filled with saline (30-130 mL) was placed in the surgical bed. The skin was temporarily closed and an ultrasound was used to confirm that the balloon to skin distance was at least 10 mm. Electronic brachytherapy via IORT was utilized to deliver 20 Gy to the balloon surface in a single fraction prior to removal of the balloon and completion of surgery. Patients were followed every six months for at least five years. Patients ranged in age from 41 to 83, with a median age of 66. Out of the 101 tumors treated, T-staging consisted of 29% Tis, 2% T1mi, 12% T1a, 24% T1b, 31% T1c and 3% T2. At a median follow up of 3.8 years, there have been two recurrences. Seroma formation was reported in 26 (26%) patients. Asymptomatic seromas were observed in 11 (11%) patients. Of the patients with symptomatic seromas, 11 (11%) required one or more aspirations. No patients required surgical excision of a seroma. Chi-squared analysis was performed for nominal variables (stage, histology, grade, proliferative rate, receptor status, margin status, tumor location) and binary logistic regressions for continuous variables (age, primary tumor size, and cavity size) with regards to risk of seroma formation. None of these reached statistical significance. Infection risk in patients with seroma was greater than in those without seroma (30.8% vs 12.0% respectively; p=0.04 using Fisher's exact test). Seroma formation was not associated with a risk of re-excision or readmission. IORT is a convenient and well-tolerated treatment option for the appropriately selected woman undergoing partial breast irradiation. Rates of seroma formation are similar to rates reported for multiple fraction catheter based systems.