The relationship between high absolute lymphocyte counts and favorable prognosis in eribulin therapy is seen in first-line chemotherapy for metastatic breast cancer: Combined analysis of two phase 2 studies

Abstract

Purpose: While the absolute lymphocyte count (ALC) and neutrophil-to-lymphocyte ratio (NLR) are associated with prolonged progression-free survival (PFS) and overall survival (OS), the influence of previous chemotherapy on blood cell counts may necessitate an evaluation of baseline ALC and NLR in patients receiving first-line chemotherapy. Methods: Patients with human epidermal growth factor receptor 2 (HER2)-negative metastatic breast cancer (MBC) who received first-line eribulin chemotherapy in two phase 2 trials (BIRICHEN and OMC-BC 03) were retrospectively analyzed. HER2-negative MBC patients who received first-line chemotherapy other than eribulin (treatment of physician’s choice; TPC) at the Osaka Medical and Pharmaceutical University Hospital between March 2013 and March 2017 were also analyzed for comparison. Results: In the eribulin group, the median OS (mOS) was 30.9 and 17.8 months in the high-(H-)ALC (≥1500/μL; n=33) and low-(L-)ALC (<1500/μL; n=26) groups, respectively (hazard ratio [HR], 0.52; 95% confidence interval [CI]: 0.27-1.01), whereas it was 30.9 months and 15.4 months in the L-NLR (<2.5; n=23) and H-NLR (≥2.5; n = 36) groups, respectively (HR, 0.49; 95% CI: 0.25-0.95). In the TPC group, neither ALC nor NLR was associated with OS or PFS extension. After propensity-score matching, the mOS in the eribulin group was 32.0 and 19.6 months, respectively, in the H- and L-ALC groups (HR, 0.43; 95% CI: 0.18-0.99), while OS in the L- and H-NLR groups showed no significant differences in the eribulin group (HR, 0.65; 95% CI: 0.27-1.58). Conclusions: ALC is a prognostic marker for first-line eribulin chemotherapy, but not for other agents.