Curative-intent stereotactic ablative body radiation, surgery, and systemic therapy in non-osseous oligometastatic breast cancer.

BACKGROUND

Stereotactic ablative body radiation (SABR), combined with systemic therapy (ST), is increasingly used to improve survival in oligometastatic breast cancer (OMBC).

METHODS

Patients with no brain or bone metastases on whole-body PET-CT received curative-intent local and systemic treatment, including SABR to metastatic site. Doses were: liver (45-50 Gy/5 fractions), peripheral lung (54 Gy/3fractions), central lung (60 Gy/8fractions), lymph nodes (30 Gy/3fractions), and peritoneal deposits (45 Gy/5fractions). Response was assessed at 3 months (RECIST v1.1); pain, gross tumour volume (GTV), planning target volume (PTV), and toxicity (CTCAE) were documented.

RESULTS

From Dec 2021 to Mar 2025, 39 patients (42 sites; median age 47) were treated: liver (17), lung (14), nodes (5), other (6). At a median follow-up of 23.9 months, median PFS was 16.3 months (95% CI: 10.3-24.1); median OS was not reached; restricted mean OS for the cohort was 89.2 months. Twenty-eight patients were alive, 11 died, two were lost to follow-up. Subtypes included TNBC (36%) and HER2+ (33%), luminal B (23%). Univariate analysis showed older age, smaller PTV, and higher BED10 improved PFS; multivariate analysis confirmed age (HR 0.20, p = 0.006), PTV (HR 6.57, p = 0.001), and luminal subtype. Most common toxicity: grade 2 pain flare and hepatitis (10%).

CONCLUSION

Curative-intent treatment with SABR for visceral OMBC offers promising survival outcomes. Molecular subtyping may aid treatment selection.

CLINICAL TRIAL NUMBER: Not applicable.