Association between platelet-to-lymphocyte ratio and outcomes in HER2-positive advanced breast cancer patients treated with pyrotinib: a retrospective study

Background: Peripheral blood biomarkers have been reported to be associated with the prognosis of breast cancer (BC) patients, but a few findings remain controversial. This study aimed to explore the correlation between peripheral blood indicators and treatment outcomes in human epidermal growth factor receptor 2 (HER2)-positive advanced BC patients treated with pyrotinib.Methods: This was a retrospective cohort study including 156 HER2-positive advanced BC patients who treated with pyrotinib between March 2019 and May 2021. The baseline clinical characteristics including age, hormone receptor (HR) status, Ki-67, sites of metastasis, antitumor therapies and peripheral blood parameters including neutrophil to lymphocyte ratio (NLR), platelet to lymphocyte ratio (PLR), monocyte to lymphocyte ratio (MLR), the product of neutrophil, platelet, and monocyte counts divided by lymphocyte count [pan-immune-inflammation value (PIV)] were collected. Tumor response was assessed every two cycles during treatment period. Follow-up was performed every 2 months to record survival status. All patients were followed up until death or time of data lock.Results: Low PLR was associated with better disease control rate (P=0.005). Univariate analysis showed that high MLR (P=0.004), PLR (P=0.003), or PIV (P=0.02), low lymphocyte count (P=0.025), more than two metastatic sites (P<0.001), and presence of liver metastasis (P<0.001) or brain metastasis (P<0.001) were associated with poor progression-free survival (PFS). Multivariate analysis showed that only high PLR was an independent factor for poor PFS [hazard ratio =0.63; 95% confidence interval (CI): 0.41-0.97; P=0.038]. For overall survival (OS), univariate analysis showed that high NLR (P=0.001), MLR (P=0.005), PLR (P<0.001), or PIV (P=0.018), more than two metastatic sites (P=0.001), presence of liver metastasis (P=0.004) or brain metastasis (P=0.007), and pyrotinib monotherapy (P=0.036) were associated with worse OS. Multivariate analysis showed that PLR (hazard ratio =0.37; 95% CI: 0.14-0.94; P=0.037), number of metastatic sites (hazard ratio =2.84; 95% CI: 1.02-7.94; P=0.046) and treatment regimens (hazard ratio =0.15; 95% CI: 0.03-0.73; P=0.019) were independent factors.Conclusions: High PLR is associated with poor treatment response and is an independent unfavorable prognostic factor in HER2-positive advanced BC patients treated with pyrotinib. The findings herein indicate that patients with higher PLR are less likely to benefit from pyrotinib-based therapy and may be helpful in identifying the effective population in clinical practice.