Conclusions
The expression of PD-1 and PD-L1 is discordant across patient-matched ccRCC tumors, with higher expression in primary tumors. Higher PD-1 expression was associated with metastatic location and lower cancer-specific survival. If validated, these results highlight the importance of evaluating these biomarkers in metastatic tissue specifically.
Methods
We analyzed PD-1 and PD-L1 using immunohistochemistry in patient-matched primary and metastatic tumors from 110 ccRCC patients. Concordance was assessed among longitudinal metastatic tumors, as well as across patient-matched primary and metastatic tumors. Cox proportional hazards regression was used to evaluate the associations of metastatic tumor expression with cancer-specific survival.
Results
We observed inter-metastatic tumor heterogeneity of PD-1 in 25 (69%) of the 36 patients and of PD-L1 in seven (19%) patients. Concordance between patient-matched primary and metastatic tumors was 73% (Kappa = 0.16, 95% CI: -0.003-0.32). Similarly, concordance of PD-L1 between metastatic and patient-matched primary tumors was 78% (Kappa = 0.27, 95% CI: 0.09-0.46). Both markers demonstrated higher expression in primary vs metastatic tumors. Metastatic tumor expression of PD-1 was significantly associated with metastatic location (P < .0001) and ccRCC-specific survival (HR = 2.15, 95% CI: 1.06-4.36, P = .035). Conclusions: The expression of PD-1 and PD-L1 is discordant across patient-matched ccRCC tumors, with higher expression in primary tumors. Higher PD-1 expression was associated with metastatic location and lower cancer-specific survival. If validated, these results highlight the importance of evaluating these biomarkers in metastatic tissue specifically.