Systemic immunity markers are associated with clinical outcomes of atezolizumab treatment in patients with triple-negative advanced breast cancer: a retrospective multicenter observational study.

Immune checkpoint inhibitors (ICI) are reportedly efficacious against triple-negative breast cancer (TNBC) and are now recommended as first-line therapy. Systemic immunity markers, the absolute lymphocyte count (ALC) and the neutrophil-to-lymphocyte ratio (NLR), have been identified as predict ICI efficacy in patients with various cancers. We retrospectively enrolled 36 TNBC patients who received atezolizumab treatment between September 2019 and May 2021 at eight Japanese medical institutions. We evaluated systemic immunity markers, including dynamic changes in these markers, as predictors of survival benefit derived from atezolizumab treatment. Median time-to-treatment failure (TTF) and overall survival (OS) were 116 days and "not reached", respectively. Patients with low NLR at baseline and decreased NLR at the start of the second cycle (SO2nd) had significantly longer OS than those with high NLR at baseline and increased NLR (SO2nd) (log-rank P < 0.001 and log-rank P = 0.049, respectively). Multivariate analyses identified high ALC at baseline and decreased NLR (SO2nd) as independent predictive markers for longer TTF (P = 0.043 and P = 0.002, respectively), and low NLR at baseline and decreased NLR (SO2nd) as independent predictive markers for longer OS (P < 0.001 and P = 0.013, respectively). The safety profile was consistent with those of previous trials. This retrospective multicenter observational study showed the clinical efficacy and safety of atezolizumab treatment. Furthermore, systemic immunity markers, including their dynamic changes, were found to be associated with clinical outcomes of atezolizumab treatment in patients with advanced or metastatic TNBC.