Tolerance and Outcomes of Partial Breast Radiation in a Community-based Setting

For women with early stage, node negative breast cancer undergoing breast conservation, guidelines have shifted towards recommending partial breast radiation (PBI) rather than whole breast radiation. However, application of PBI has been somewhat slow in some settings, particularly in the United States. In this retrospective study, we sought to evaluate tolerance, toxicity and outcomes in women who elected PBI in a large community-based practice.

A total of 180 women aged 40 years or older were treated with PBI at our institution between 2018-2022 after undergoing lumpectomy with negative margins. Radiation dose regimens included 40 Gy in 15 fractions (Fxs), 35 Gy in 10 Fxs, 30 Gy in 5 Fxs, and 26 Gy in 5 Fxs, all delivered once daily using external beam radiation therapy. Outcome data collected included short and long term toxicities, local recurrence, regional recurrence, distant recurrence, death, endocrine therapy compliance, and follow-up time.

Median follow up was 50.5 months and median age was 65.5 years. Most patients (80%) had invasive cancer and 20% had ductal carcinoma in situ. Of those who were ER+, 89.3% initiated endocrine therapy and 22% stopped endocrine therapy prematurely. Short term grade 2 side effects were noted in 8 women (4.4%). There were no grade 3+ side effects. There were two (1.1%) grade 2 long term side effects consisting of persistent breast pain, and both were in women who received 30Gy/5Fx. There was one local recurrence, diagnosed at 70 months after completion of radiation and one regional and distant metastatic recurrence at 34 months.

Partial breast radiation in this large community-based setting was very well tolerated, with minimal long-term side effects and only one local recurrence.