Electronic Brachytherapy at the Time of Breast Conservation Surgery for Early-Stage Breast Cancer: Early Follow-Up Results of a Nonrandomized, Multicenter Trial

Abstract

To describe early follow-up results of a trial of single-fraction, intra-operative radiation therapy (IORT) delivered with an electronic brachytherapy system immediately following surgical resection for treatment of early-stage breast cancer. To date, 1,028 participants have been enrolled in this open label, single-arm, prospective, non-randomized trial at 28 hospitals in the USA (27) and Portugal (1). 1,023 participants with biopsy-proven ductal carcinoma in situ (DCIS) or invasive ductal carcinoma who met the inclusion criteria underwent lumpectomy followed by IORT to the lumpectomy cavity. A presterilized lead shield was placed on the chest wall and a balloon applicator suitable to the surgical bed was placed in the lumpectomy cavity and inflated with saline (30-75 cc). Balloon surface-to-skin distance of ≥ 1.0 cm was confirmed by ultrasound. Single-fraction IORT (20 Gy) was delivered at the balloon applicator surface with a mean radiation treatment time of 11.3 minutes. Following IORT, balloon was deflated and removed along with lead shielding, and surgical site was sutured. The prespecified primary outcome of this 10-year follow-up study is ipsilateral breast tumor recurrence at 5 years. Prespecified secondary outcomes include 10-year recurrence and cosmesis (Harvard Scale). Median follow-up time was 1.2 years with 320, 102, and 10 participants completing 2-, 3-, and 4-year follow-up, respectively. Mean age at enrollment was 66 years (range 41-93). 246 participants had DCIS and 777 had invasive ductal carcinoma. DCIS nuclear grades were high (82), intermediate (119), or low (45) with three identified as bilateral. Invasive cancers were Grade 1 (318) including two bilateral cases, Grade 2 (340) with one bilateral case, Grade 3 (105) with two bilateral cases, or no Grade (14). Mean tumor size was 12.01 ± 10.8 mm. Cosmesis was excellent in 100% of participants at 4-year follow-up and excellent to good in 94% and 91% of participants at 2- and 3-year follow-up, respectively. The number of reported adverse events (AEs) that were Grade 2 or higher was 169 (9%). Seroma, breast induration, erythema, breast fibrosis, and breast pain were the most frequent AEs. There were ten deaths, none of which were breast cancer related. There were six ipsilateral breast recurrences and three new contralateral breast cancers. Single-fraction IORT using an electronic brachytherapy system following breast conservation surgery may be a promising treatment option for select early-stage breast cancer patients. Early findings from this multicenter trial suggest that the short and convenient course of radiation therapy has low morbidity, excellent to good cosmetic results, and a low rate of high-grade adverse events and recurrences.