Between 5% and 20% of patients with breast cancer (BC) experience locoregional recurrence (LRR). Managing LRR in previously irradiated areas is particularly challenging. We evaluated the toxicity and efficacy of stereotactic body re-irradiation in this context.

This was a single-center retrospective study conducted between January 2009 and December 2022. It included patients who underwent stereotactic re-irradiation for LRR of BC. We assessed toxicity, local control (LC), progression-free survival (PFS), and overall survival (OS).

Eighteen patients were included. The median dose of the initial radiotherapy (RT) was 60 Gy (range: 50–68 Gy). Recurrences occurred in level I-II nodes (n = 10), internal mammary nodes (IMN; n = 4), level III (n = 2), and level IV (n = 2). The median interval between the two irradiations was 11 years (range: 1–24 years). The most commonly used stereotactic re-irradiation regimens were 6 × 6 Gy and 3 × 9 Gy. Median D50% to the GTV and PTV was 36.9 Gy (32–41.8 Gy) and 35.7 (30.2–40.6 Gy), respectively. The D0.035 cc to the brachial plexus was 11.2 Gy (range, 4–33.6 Gy). With a median follow-up of 4.5 years from the start of SRT (IQR: 2.0‒7.5), no radiation-induced brachial plexopathy was observed. The cumulative incidence of locoregional recurrence was 56.4% (95%CI: 30.8–75.6) at 2 years. The 5-year overall survival (OS) rate was 75.5% (95CI: 39.7–91.8), with most deaths attributed to distant metastases.

Stereotactic re-irradiation is a well-tolerated treatment option for LRR in breast cancer. Particular care should be taken to minimize the dose to the brachial plexus. While local control is acceptable, the risk of further regional recurrence remains high.