In a study using next-generation sequencing (NGS) for circulating tumor DNA (ctDNA) analysis, APOBEC was verified to be enriched in both high bTMB and low bTMB HR+/HER2− patients, further validating that APOBEC can be used as a biomarker by testing blood to predict response to ICI therapy and to decide whether to combine ICI with chemotherapy (Davis et al., 2023). This evidence concerns the gene ERBB2 and neoplasm.