Does Intraoperative Radiation Therapy Provide Comparable Local Control to Partial Breast Irradiation in Patients...

Partial breast irradiation (PBI) offers the ability for smaller treatment volumes, reduced toxicities, and shorter treatment duration. One alternative to PBI is intraoperative radiation (IORT), though local control outcomes are mixed. The purpose of this analysis is to compare outcomes with PBI and IORT, including in those patients suitable for omission of radiation therapy.

Patients with early stage breast cancer who received PBI or IORT between 2011 and 2021 were evaluated. PBI patients received 30 Gy in 5 fractions and IORT patients received 20 Gy in 1 fraction using a 50 kv device. Patients with less than 2 years of follow-up were excluded from the analysis.

A total of 245 patients with a median age of 67 years received PBI, and 202 patients with a median age of 70 years received IORT. Median follow-up was 3.5 years for PBI and 6.5 years for IORT; 5-year local control (LC) was 99.6% for PBI versus 94.7% for IORT (p = 0.01). For patients meeting PRIME II criteria, 5-year LC was 99.2% for PBI versus 94.1% for IORT (p = 0.09), while for patients meeting CALGB 9343 criteria, 5-year LC was 100% for PBI versus 94.8% for IORT (p = 0.11).

IORT has worse local control as compared with 5-fraction PBI, even among patients eligible for omission of RT. Given concerns regarding compliance with endocrine therapy, for patients eligible for omission of RT, 5 fraction PBI offers a convenient treatment option to optimize local control, while IORT has a limited role as monotherapy, consistent with current guidelines.