We thank Professor Torlakovic for her comments and interest in our recent work on the concordance of PD-L1 assays in gastric cancer (GC) [
1]. We agree with the author that the designated antibody companion diagnostic (CDx) for the respective immune checkpoint inhibitors (ICIs) have established analytical performances and should be the standard-of-care in predicting treatment response to ICIs. However, current regulatory approvals for ICI in GC treatment do not specify the choice of CDx to be used. Furthermore, with an increasing number of approved ICIs, there has been a corresponding increase in the number of designated CDx [
2,
3]. …
