Long-Term Results of a Prospective Multicenter Trial of APBI with Photon IORT

The aim of the present study is to analyze, for the first time, the results of a large prospective academic multicenter trial of partial breast irradiation (PBI) with exclusive photon intraoperative radiation therapy (ph-IORT) in early breast cancer patients, focusing on ipsilateral breast tumor recurrence. The secondary endpoints were (a) incidence of regional/distant recurrence, (b) survival, and (c) toxicity.

From January 2013 to December 2022, patients with low-risk TARGIT-A criteria invasive breast cancer were included in a prospective academic multicenter study of exclusive PBI with ph-IORT during breast-conserving surgery, conducted in three university hospitals in Las Palmas (Hospital Universitario Insular, Hospital Universitario Materno-Infantil, and Hospital Universitario de Gran Canaria Dr. Negrín).

Three hundred and twelve patients were included in the study. The mean age at diagnosis was 62 years (46-88). All tumors were classified as luminal molecular profile. No patient received supplementary external beam radiotherapy. Four patients developed ipsilateral breast tumor recurrence (IBTR) at 19, 29, 43, and 62 months of follow-up. Seventeen patients died of intercurrent diseases, and there were only 2 breast cancer-related deaths at 68 and 95 months, respectively. With a median follow-up of 78 months (7-140), actuarial 5-year freedom from local relapse and cancer survival rates were 98.9% and 100%, respectively. No patient developed early or late grade-3 toxicity.

Partial breast irradiation with ph-IORT is a feasible, safe, and useful treatment in early breast cancer patients after BCS. A longer follow-up is needed to confirm the present results.