Expression of PD-1 and PD-L1 increase in consecutive biopsies in patients with classical Hodgkin lymphoma

High expression of programmed death receptor 1 (PD-1) and its ligand (PD-L1) by leukocytes in primary classical Hodgkin lymphoma (cHL) is associated with inferior outcome. However, it is unclear how expression varies during disease progression, and in the event of relapse. Our aim was to study PD-1 and PD-L1 in consecutive biopsies from untreated and treated cHL patients. We screened pathology registries from 3500 cHL patients. Eleven patients had a diagnostic cHL biopsy and a previous benign lymph node biopsy reclassified as cHL when reviewed and designated as the untreated. Thirty patients had a primary and a relapse biopsy, designated as the treated. Biopsies were immunostained to detect PD-1+ and PD-L1+ leukocytes, and PD-L1+ tumor cells. In the untreated, none of the markers were statistically significantly different when biopsies 1 and 2 were compared. In the treated, 19, 22, and 18 of 30 cases had increased proportions of PD-1+ leukocytes, PD-L1+ leukocytes and PD-L1+ tumor cells, respectively, and were all statistically significantly increased when primary and relapse biopsies were compared. PD-1 and PD-L1 most likely increase due to primary treatment with chemotherapy and radiotherapy, which could have implications regarding treatment with PD-1 inhibitors.