Expression of PD-1 and PD-L1 in Anaplastic Thyroid Cancer Patients Treated With Multimodal Therapy: Results From a Retrospective Study

Context: Anaplastic thyroid cancer (ATC) is rare and a highly fatal malignancy. The role of programmed death-1 (PD-1) and programmed death ligand-1 (PD-L1) as prognostic and/or predictive markers in ATC is unknown. Objective: Multimodal therapy offers the best chance at tumor control. The objective of this study was to detect potential associations of PD-1/PD-L1 axis variables with outcome data in ATC. Design: Retrospective study of a uniformly treated cohort. Setting: Single institution retrospective cohort study. Patients or Other Participants: Sixteen patients who received intensity-modulated radiation therapy (15 had preceding surgery) were studied. Main Outcome Measure: Patients treated with multimodal therapy were followed and assessed for overall survival (OS) and progression-free survival (PFS). Results: All samples demonstrated PD-1 expression in inflammatory cells whereas tumor cells were primarily negative. PD-L1 was expressed on ATC tumor cells in most samples and showed mainly membranous staining. High PD-1 expression (> 40% staining) in inflammatory cells was associated with worse overall survival (OS; hazard ratio, 3.36; 95% confidence interval, 1.00 to 12.96; P < 0.05) and trended toward worse PFS, whereas high PD-L1 expression in tumor cells (>33% staining) trended toward worse PFS and OS. Conclusion: PD-1/PD-L1 pathway proteins are highly expressed in ATC tumor samples and appear to represent predictive markers of PFS and OS in multimodality-treated ATC patients.