Factors Associated with the Selection of First-line Bevacizumab plus Chemotherapy and Clinical Response in HER2-negative Metastatic Breast Cancer: ONCOSUR AVALOX Study.

Aim: To evaluate factors associated with the selection of first-line bevacizumab plus chemotherapy and clinical response in HER2-negative metastatic breast cancer (MBC) in clinical practice in Spain.

Patients And Methods: All consecutive adult female patients with HER2-negative MBC who had received first-line bevacizumab plus chemotherapy for at least 3 months were enrolled in the present study.

Results: A total of 292 evaluable patients were included; 25% had triple-negative breast cancer (TNBC) and 75% had hormone receptor-positive breast cancer (HRPBC). Nearly 40% of patients had ≥3 metastatic sites, mainly located in the bone (48%) and liver (40%). Bevacizumab was mostly combined with paclitaxel (67.1%). ER-positive tumors were only identified as an independent factor associated with the choice of treatment (odds ratio (OR): 0.538; p=0.02). The overall response rate (ORR) was 63.7% (TNBC: 57.5%; HRPBC: 65.9%). Patients aged 36-50 years (OR: 3.03; p=0.028) and those with metastases at sites other than the bone (OR: 0.38; p=0.001) and ≥3 metastatic sites (OR: 1.41; p=0.018) were more likely to achieve objective responses.

Conclusion: First-line bevacizumab plus chemotherapy, mainly paclitaxel, is an effective and well-tolerated treatment option for HER2-negative MBC, particularly in more aggressive disease.