Prognostic and predictive factors of eribulin efficacy in heavily pretreated patients affected by metastatic breast cancer: correlation with tumor biology and previous therapies

BACKGROUND: Eribulin mesylate is currently approved in the United States and Europe for the treatment of metastatic breast cancer (MBC). SCOPE: The objective of this retrospective study is to find specific predictive criteria related to patient or tumor characteristics in order to select patients that might benefit the most from eribulin and define the correct treatment sequence. FINDINGS: Forty-four patients with MBC who received eribulin in third or subsequent lines of therapy in a single Italian center were considered eligible. Patients were stratified by body mass index, hormonal/HER2 status, and previous therapies. Primary endpoint was progression free survival (PFS), whereas secondary endpoint was disease control rate (DCR). A longer PFS was found in patients with hormone-positive tumors (p=0.0051), in HER2-negative cases (p=0.037), and in overweight patients (p=0.0015). No difference in efficacy was observed when eribulin was administered in third or subsequent lines of therapy. Significantly longer PFS (p<0.0001) and higher DCR (p=0.035) were achieved by patients previously treated with paclitaxel-bevacizumab in comparison to those pretreated with other drug combinations or with anthracyclines. Prior treatment with nab-paclitaxel seems to have a detrimental effect on PFS (p=0.0008). CONCLUSION: Hormone and HER2 status seems a good predictive and prognostic indicator of response to eribulin. Efficacy seems independent from the number of prior therapies, and it is not influenced by prior endocrine treatments and anthracyclines-containing regimens. On the other hand, sensitivity to a prior treatment with paclitaxel-bevacizumab might be predictive of response to eribulin.