Beyond the first dose: Systematic review on external beam radiotherapy for locoregional breast cancer recurrence

The optimal management of locoregional breast cancer recurrence after prior radiotherapy remains challenging. Reirradiation (ReRT) may allow repeat breast-conserving surgery as an alternative to mastectomy; however, prospective evidence is scarce, and existing data are largely retrospective, with the strongest support for brachytherapy. Despite this, external beam reirradiation (EBreRT) is widely used because of its availability. This systematic review evaluated the feasibility, oncologic outcomes, toxicity, and patient-reported outcomes of external-beam ReRT for locoregional breast cancer recurrence.

Following the PRISMA guidelines (PROSPERO CRD420251003760), seven databases were searched until November 2025 to identify studies evaluating adjuvant external beam reirradiation for locoregional breast cancer recurrence. The outcomes of interest included disease control, survival, toxicity, and patient-reported outcomes, which were summarized descriptively.

Twenty-four studies published between the mid-1980s and 2024, comprising 1252 patients, were included; most were retrospective, heterogeneous, single-institution cohorts with moderate quality. Reirradiation was predominantly delivered as partial-breast photon-based EBreRT using conventional fractionation.

Evidence on EBreRT for locoregional breast cancer recurrence remains insufficient to define optimal dose regimens, treatment intervals, or standardized patient selection criteria, as the available studies are predominantly retrospective and heterogeneous. Nevertheless, the available data suggest that EBreRT may be a feasible therapeutic option, provided that careful case-by-case patient selection is applied.