Surgical resection plus radiotherapy reduces radiation dermatitis risk without survival benefit in metastatic breast cancer: a retrospective cohort study

The role of local interventions (surgery/radiotherapy) targeting the primary tumor in improving survival among patients with metastatic breast cancer (MBC) remains controversial. This retrospective cohort study compared two local treatment modalities—surgical resection combined with radiotherapy (S+R) versus radiotherapy alone (R)—in terms of toxicities and prognosis in treatment-naive MBC patients, to evaluate the survival benefit and safety profile of these approaches for primary tumor management in MBC.

Using a retrospective cohort design, we analyzed 89 de novo MBC patients treated at Department of Oncology, Affiliated Tumor Hospital of Guizhou Medical University, between 2010 and 2025 (42 cases in the R group and 47 cases in the S+R group). Propensity score matching (PSM) with a caliper value of 0.2 was employed to balance baseline characteristics, yielding 62 matched patients (31 per group). The primary endpoints were overall survival (OS) and progression-free survival (PFS). Secondary endpoints included treatment-related adverse events (toxicity), local control (LC), and time to disease progression (TTP). Statistical analyses were performed to evaluate survival outcomes (OS, PFS, TTP) and toxicity indicators (radiation-induced skin fibrosis, radiation dermatitis, and ipsilateral limb lymphedema).

Baseline characteristics were well balanced after matching (all P>0.05). The median follow-up was 56.2 months. No vs significant differences were observed between the S+R and R groups in median OS (55.4 vs 56.2 month, P=0.738), PFS (49.2 vs 37.0 months, P=0.959), or TTP (49.2 vs 37.5 months, P=0.808). No local recurrence occurred in either group (LC: 100% vs 100%). Univariate and multivariate Cox regression analyses identified the triple-negative subtype as an independent risk factor for OS (HR=15.451, 95%CI: 1.253 to 190.579, P=0.033), and cN stage as an independent risk factor for PFS (HR=1.489, 95%CI:1.006 to 2.202, P=0.046). For safety outcomes, compared with R, S+R yielded a significantly lower rate of grade 3 dermatitis (0 vs 12.9%, P=0.001), with comparable rates of fibrosis (3.23% vs 9.68%) and lymphedema of the affected limb (12.90% vs 6.45%) (both P>0.05).

Compared with R, S+R does not significantly improve survival outcomes in MBC patients, but it is associated with lower risk for radiation dermatitis. Triple-negative subtype and cN stage are identified as important adverse prognostic factors in MBC.