Increasing survival of metastatic breast cancer through locoregional surgery.

Background: Surgery for the primary tumor in metastatic breast cancer is usually not recommended, assuming that local therapy provides no advantage. Recent reports suggest a survival improvement after locoregional treatment, but this is still controversial. We aimed to evaluate the effectiveness of locoregional treatment in primary metastatic breast cancer and to determine associated factors.

Methods: A retrospective analysis of 39 women with de-novo metastatic breast cancer at La Paz University Hospital, from January 2012 to June 2016, grouped by locoregional treatment (n=23) or not (n=16). Multivariate assessment of prognostic factors was performed using Cox regression analysis.

Results: Mean tumor size was 6 cm. Eighteen patients (46.2%) had multifocal tumors, 29 (74.4%) multicentric and 10 (25.7%) bilateral breast cancer. Eighteen patients (46.2%) had an oligometastatic disease and 21 (53.8%) multiorgan metastatic disease. The average time from diagnosis to surgery was 7.7 months, without delay in the start of systemic treatment compared to the no-surgery group. The main surgical procedure was mastectomy in 18 (78.3%) patients. Half of the patients survived 48 months (95% CI: 39-57). In the multivariate analysis, we have not detailed differences in survival by age, chemotherapy, neoadjuvancy, number of systemic treatment lines, radiotherapy, and tumor histology or grade. However, surgery (HR=0.2; 95% CI: 0.07-0.57) and high tumor burden (HR=2.96, 95% CI: 1.23-7.13) have acted as a protective and a risk factor respectively.

Conclusions: Our cohort supports that locoregional treatment in selected patients with de-novo MBC significantly improved survival, so it might be considered in combination with systemic therapy.