Efficacy of Single‐Agent Chemotherapy for Patients with Advanced Invasive Lobular Carcinoma: A Pooled Analysis from Three Clinical Trials

AbstractBackground.Data on the efficacy of chemotherapy regimens in patients with advanced invasive lobular carcinoma (ILC) of the breast are limited. We investigated the efficacy of single‐agent eribulin for the treatment of advanced ILC when compared with invasive ductal carcinoma (IDC).Patients and Methods.Results from the eribulin arms of two phase III studies (305 [EMBRACE] and 301) and a single‐arm, phase II study were pooled. The studies involved patients with metastatic breast cancer who had previously received treatment with an anthracycline and a taxane. In all three studies, the dose of eribulin mesylate was 1.4 mg/m2 given on days 1 and 8 of a 21‐day cycle. Overall survival (OS), progression‐free survival (PFS), and response rates in patients with ILC were assessed and compared with data from patients with IDC.Results.In total, 1,152 patients were included in this analysis (118 patients with ILC and 1,034 patients with IDC). Median OS was similar in patients with ILC and IDC (13.4 vs. 13.5 months; hazard ratio [HR], 1.10; 95% confidence interval [CI], 0.87–1.38); as was median PFS (4.1 vs. 3.6 months; HR, 0.91; 95% CI, 0.72–1.14). There were no major differences in response rates between the two groups.Conclusion.This retrospective analysis suggests that eribulin demonstrates similar efficacy in patients with ILC and IDC with metastatic disease who have previously received an anthracycline and a taxane.Implications for Practice.Data on the efficacy of chemotherapy regimens in patients with advanced invasive lobular carcinoma (ILC) of the breast are limited. This pooled retrospective analysis of three clinical studies demonstrates that the magnitude of benefit of eribulin in the metastatic setting did not differ between patients with ILC versus invasive ductal carcinoma (IDC), even when restricting for patients with estrogen receptor‐positive/HER2‐negative IDC.

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