Few studies have so far described the conversion of programmed death-ligand 1 (PD-L1) after treatment. In particular, the effect of nivolumab on the PD-L1 expression has never been reported. We investigated the changes in PD-L1 expression after chemotherapy and nivolumab treatment and herein describe the detailed clinical course.

We retrospectively examined the PD-L1 expression in resected specimens and in the re-biopsy specimens of patients with non-small cell lung cancer by immunohistochemical analysis.

Four patients underwent a re-biopsy after treatment. Of those, three showed positive conversion of the PD-L1 expression. One patient underwent a re-biopsy after chemotherapy and nivolumab treatment, and the other two cases underwent a re-biopsy after chemotherapy, radiotherapy and nivolumab treatment.

These cases suggest the positive conversion of PD-L1 expression after treatments including nivolumab, suggesting that PD-L1 expression must be assessed in not only the resected specimens, but also in the re-biopsied ones.