To evaluate the expression of programmed cell death-ligand 1 (PD-L1) in anal cancer. In a retrospective cohort analysis, subjects with squamous cell carcinoma of the anal canal were tested for PD-L1 expression, then followed for recurrence and survival. Crude recurrence rates (CRRs), crude mortality rates (CMRs), and crude event rates (CERs) were assessed for PD-L1-dependent differences using Poisson regression. All 3 types of crude rate were expressed as the number that occurred per hundred person-years (hPY) of follow-up. Samples from 41 subjects were evaluated for PD-L1 expression; 23 (56%) were positive. Subjects with PD-L1-expressing versus PD-L1-negative tumors respectively had CRRs of 30.8 versus 12.1 recurrences/hPY (P=0.082), CMRs of 16.7 versus 12.0 deaths/hPY (P=0.47), and CERs of 39.2 versus 16.9 events/hPY (P=0.069). PD-L1 positivity was associated with worse CRR and CER, and marginally worse CMR. The effect on progression-free and overall survival needs to be validated in a study with a larger sample size.
