Local ablative treatment and continuation of systemic therapy for oligoprogressive metastatic breast cancer: a retrospective cohort study.

INTRODUCTION

Patients with metastatic breast cancer (MBC) typically receive palliative systemic therapy until unmanageable toxicity or progression, at which point treatment is changed. However, this approach may be suboptimal for patients with oligoprogression (OLP), defined as progression in one or few metastatic sites while other metastases remain controlled. Local ablative therapy (LAT) targeting oligoprogressive lesions may allow continuation of otherwise effective systemic treatment.

METHODS

We searched the registry of a tertiary cancer center for patients with MBC and oligoprogression diagnosed between 2014 and 2024. Eligible patients had stable or responding disease for at least six months prior to OLP detection, LAT within six months after OLP detection, and continuation of the same systemic treatment. Endpoints were progression-free survival after LAT, time to first subsequent systemic therapy and overall survival.

RESULTS

Thirty-four patients met the inclusion criteria. Most had 1-2 oligoprogressive lesions, most commonly involving bone, lymph nodes, or the primary breast tumor. LAT consisted of radiotherapy (62%), surgery (32%), or both (6%). Local control at the site of ablative therapy was 76% (95% CI, 59%-89%). Median progression-free survival after LAT was 14.6 months (95% CI, 8.26-20.5), median time to first subsequent therapy was 20.9 months (95% CI, 14.9-48.9) and median overall survival was 96.4 months (95% CI, 66.8-NA).

CONCLUSION

LAT was associated with prolonged disease control and delayed the switch to subsequent therapy. However, conclusions regarding survival benefit are limited by the retrospective design, lack of control group, and possible selection of patients with favorable prognosis. A prospective randomized trial is therefore warranted.