Baseline absolute lymphocyte count as a prognostic indicator in advanced or metastatic breast cancer: a systematic review and meta-analysis

This study used meta-analysis to examine the role of baseline absolute lymphocyte count (ALC) in the prognosis of advanced breast cancer (ABC) or metastatic breast cancer (MBC). A comprehensive search encompassing PubMed, The Cochrane Library, Embase, and Web of Science databases was undertaken to identify and screen literature based on predefined inclusion and exclusion criteria. Progression-free survival (PFS), time to treatment failure (TTF), post-progression survival (PPS), and overall survival (OS) were selected as outcome measures. A meta-analysis of 14 studies, involving 2,540 patients and employing Review Manager 5.3 and Stata 14.0, was conducted. Notably, 12 of these studies originated from Japan. The findings indicated that patients with ABC or MBC exhibiting high ALC had significantly improved PFS, TTF, PPS (hazard ratio [HR] = 0.53, 95% confidence interval [CI]: 0.45-0.62, P < 0.00001; HR = 0.57, 95% CI: 0.51-0.64, P < 0.00001), and OS (HR = 0.44, 95% CI: 0.33-0.58, P < 0.00001; HR = 0.68, 95% CI: 0.60-0.77, P < 0.00001) juxtaposed with low ALC individuals. These findings were corroborated by both univariate and multivariate analyses. Furthermore, subgroup analysis based on breast cancer subtype unveiled that high ALC was associated with prolonged PFS (HR = 0.35, 95% CI: 0.21-0.56, P < 0.0001), TTF, and PPS (HR = 0.45, 95% CI: 0.29-0.71, P = 0.0006) in both human epidermal growth factor receptor 2 (HER-2)-positive and -negative ABC or MBC patients. Additionally, high ALC correlated with prolonged OS in all BC subtypes (HR = 0.73, 95% CI: 0.61-0.88, P = 0.0008) and HER-2-negative ABC or MBC patients (HR = 0.65, 95% CI: 0.55-0.78, P < 0.00001). Subgroup analysis was conducted on chemotherapy regimens, with and without eribulin. Despite variations in chemotherapy regimens, patients with ABC or MBC and high ALC exhibited longer PFS and PPS (HR = 0.45, 95% CI: 0.30-0.67, P < 0.0001), PFS and TTF (HR = 0.39, 95% CI: 0.20-0.78, P = 0.008), and OS (HR = 0.71, 95% CI: 0.62-0.82, P < 0.00001; HR = 0.5, 95% CI: 0.35-0.70, P < 0.0001). The results of this meta-analysis suggest that baseline ALC, as an immune marker, can serve as an effective prognostic indicator for ABC or MBC.