Oral etoposide in heavily pre-treated metastatic breast cancer: results from the ESME cohort and comparison with other chemotherapy regimens.

HER2-negative metastatic breast cancer (MBC) is a common setting in which chemotherapy could be effective even in later lines of treatment. Oral etoposide has demonstrated clinical activity in this setting in small-scale studies, but its efficacy has not been compared to that of other chemotherapy regimens. We used the ESME database (Epidemiological Strategy and Medical Economics), a real-life national French multicentre cohort of MBC patients initiating therapy between 1 January 2008 to 31 December 2014. HER2-negative MBC patients who received oral etoposide as > 3rd chemotherapy line and for more than 14 days were included. Primary objective was progression-free survival (PFS); secondary objectives were overall survival (OS), and propensity-score matched Cox models including comparison with other therapies in the same setting. Three hundred forty-five out of 16,702 patients received oral etoposide and 222 were eligible. Median PFS was 3.2 months [95% CI 2.8-4] and median OS 7.3 months [95% CI 5.7-10.3]. Median PFS did not significantly differ according to the therapeutic line. The only prognostic factor for both PFS and OS was the MBC phenotype (hormone receptor-positive versus triple-negative, HR = 0.71 [95% CI 0.52-0.97], p = 0.028 for PFS and HR = 0.65 [0.46-0.92], p = 0.014 for OS). After matching for the propensity score, no differential effect on PFS or OS was observed between oral etoposide and other chemotherapy regimens administered in the same setting (HR = 0.94 [95% CI 0.77-1.15], p = 0.55 for PFS and HR = 1.10 [95% CI 0.88-1.37], p = 0.40 for OS). Oral etoposide retains some efficacy in selected heavily pre-treated patients with HER2-negative MBC, with the advantages of oral administration.