Systemic treatment with or without ablative therapies in oligometastatic breast cancer: A single institution analysis of patient outcomes

Abstract

Purpose: Local ablative treatment (LAT) is increasingly combined with systemic therapy in oligometastatic breast cancer (OMBC), without a high-level evidence to support this strategy. We evaluated the addition of LAT to systemic treatment in terms of progression-free survival (PFS) and overall survival (OS). Secondary endpoints were local control (LC) and toxicity. We sought to identify prognostic factors associated with longer OS and PFS.

Methods and materials: We identified consecutive patients treated between 2014 and 2018 for synchronous or metachronous OMBC (defined as ≤ 5 metastases). LAT included stereotactic body radiation therapy (SBRT) and volumetric modulated arc therapy (VMAT), surgery, cryotherapy and percutaneous radiofrequency ablation (PRA). PFS and OS were calculated, and Cox regression models analyzed for potential predictors of survival.

Results: One hundred two patients were included (no-LAT, n = 62; LAT, n = 40). Sixty-four metastases received LAT. Median follow-up was 50.4 months (95% CI [44.4; 53.4]). One patient experienced grade 3 toxicity in the LAT group. Five-year PFS and OS were 34.75% (95% CI [24.42-45.26]) and 63.21% (95% CI [50.69-73.37]) respectively. Patients receiving both LAT and systemic therapy had longer PFS and OS than those with no-LAT ([HR 0.39, p = 0.002]) and ([HR 0.31, p = 0.01]). The use of LAT, HER2-positive status and hormone-receptor positivity were associated with longer PFS and OS whereas liver metastases led to worse PFS.

Conclusions: LAT was associated with improved outcomes in OMBC when added to systemic treatment, without significantly increasing toxicity. The prognostic factors identified to extend PFS and OS may help guide clinicians in selecting patients for LAT.

Keywords: Breast cancer; Local ablative treatment; Oligometastases; Standard of care; Systemic treatment.

Fig. 1

Study flowchart.

Fig. 2

Progression-free survival (PFS) and overall survival according to local ablative treatment 6 months after initiation of initial treatment (landmark analysis). A: PFS analysis of groups treated with systemic treatment alone (no-LAT) (n = 64) or local ablative treatment (LAT) group (n = 26) (landmark 6-month analysis).B: OS analysis of groups treated with systemic treatment alone (no-LAT) (n = 64) or LAT (n = 26) (landmark 6-month analysis). Groups were defined according to treatments received before the landmark time and patients who progressed or were censored before the landmark time were excluded.evt: event.