Second breast conserving therapy after ipsilateral breast tumor recurrence - a 10-year experience of re-irradiation

The aim of this study is to evaluate the efficacy and toxicity of post-operative partial breast re-irradiation with multi-catheter brachytherapy after second breast conserving therapy (BCT) in patients with small, low-risk ipsilateral breast tumor recurrence (IBTR).

Between 2008 and 2018, 19 consecutive patients with low-risk IBTR (max. rpT1 cN0 cM0, Her2 negative, preferably positive hormone receptor status) who refused mastectomy were treated with salvage lumpectomy, followed by post-operative partial breast re-irradiation with multi-catheter brachytherapy. Eight patients were irradiated using PDR brachytherapy (49.8-50.4 Gy in pulses of 0.5-0.7 Gy) and 11 patients using HDR brachytherapy (34.2 Gy in fractions of 3.8 Gy or 32 Gy in fractions of 4 Gy). All patients had undergone prior BCT for their primary tumor, followed by adjuvant whole breast radiotherapy. Local control (LC), locoregional control (LRC), overall survival (OS), disease-free survival (DFS) as well as toxicity were evaluated in the present study.

After a median follow-up of 65 months following IBTR (18-120 months), only one second IBTR in 19 patients was diagnosed 77 months after re-irradiation, resulting in a LC rate of 100% at 5 years. DFS and OS rates were both 100% at 5 years following re-irradiation. Except for the above mentioned second IBTR, no regional or distant relapse was recorded. Regarding toxicity, 63% of patients developed adverse events (CTCAE grade ≤ 2), with fibrosis detected in 37% (7/19) of patients, necrosis in 11% (2/19), hyperpigmentation in 47% (9/19), and telangiectasia in 11% (2/19), respectively. No patient showed a high-grade (CTCAE grade ≥ 3) adverse event.

In case of small, low-risk IBTR, adjuvant re-irradiation using multi-catheter brachytherapy is a feasible, safe, and effective treatment method after repeated lumpectomy, and an alternative to mastectomy.