Programmed death 1 ligand (PD-L1) in solid cancers after allogeneic hematopoietic stem cell transplantation: a retrospective analysis by the Nagasaki Transplant Group.

Programmed death 1 ligand (PD-L1) is an immunomodulatory molecule expressed by cancer cells, and it has been widely demonstrated to inhibit host antitumor responses. The aim of the present study was to identify clinicopathological features associated with PD-L1 expression in the secondary solid cancers of patients after allogeneic hematopoietic stem cell transplantation. In this database of 530 patients who received allo-HSCT between 1990 and 2017, 15 developed solid cancers with a median interval of 3487 days after transplantation. Three patients had 2 different solid cancers. Eighteen solid cancer cases were identified. A multivariate analysis showed that chronic graft-versus-host disease (GVHD) was associated with an increased risk of solid cancer. The presence of chronic GVHD was observed in 8 out of 18 cases at the diagnosis of secondary malignancies. PD-L1 expression levels in cancers were significantly higher in patients with active chronic GVHD than in those without chronic GVHD (P = 0.020). Five cases of cancer that developed in the involved organs of chronic GVHD showed 30% or higher PD-L1 positivity. The present results revealed distinct PD-L1 expression in the secondary solid cancers of post-transplant patients with chronic GVHD.