To the editor,


I wish to congratulate Watanabe and their colleagues for their article [1] in which they retrospectively investigated the neutrophil-to-lymphocyte ratio and absolute lymphocyte count (ALC) in HER2–metastatic breast cancer (MBC) patients receiving eribulin and assessed the utility of eribulin re-administration for further OS improvement. They reported that ALC was identified as a predictive marker for eribulin therapy, and the readministration of eribulin is considered a valid therapeutic option for further improvement of the OS in HER2–ER + MBC patients. Receptor conversion for ER, PR, and HER2 occurs frequently in the MBC. Currently, reassessing receptor status in metastases is strongly encouraged [2]. In the current study, the authors did not mention re-biopsy rates from metastatic sites among these cases and infiltrating lymphocyte distribution around the metastatic tumors. Denkert et al. reported that increased tumor-infiltrating lymphocytes were an adverse prognostic factor for survival in luminal-HER2-negative breast cancer in a pooled analysis of 3771 patients treated with neoadjuvant therapy [3]. However, there have been no data showing any association between increased TIL in metastatic site and response to eribulin or any other chemotherapeutics in MBC in the current literature. In conclusion, one would expect that there would be positive correlation between ALC and increased TIL in MBC patients who get benefit from eribulin treatment. This issue merits further investigation.