Clinicopathologic and genomic characterization of PD-L1-positive uterine cervical carcinoma

Positive program death-ligand 1 (PD-L1) immunohistochemistry (IHC) is an approved companion diagnostic guiding the use of immune checkpoint inhibitors in uterine cervical carcinoma (CXC). The clinical and genomic features of PD-L1-positive (PD-L1^positive) CXC have not been previously described. We reviewed the clinicopathologic and molecular features of 647 CXC cases that were tested using DAKO 22C3 PD-L1 IHC and comprehensive genomic profiling during the course of clinical care. PD-L1^positive cases were defined via a combined positive score of ≥ 1. No differences were found in age, genetic ancestry, and HPV status of the PD-L1^positive (n = 548) and PD-L1^negative disease subset. The PD-L1 positivity rate varied by histologic subtype of CXC with squamous cell carcinoma (SCC) having a PD-L1 positivity rate of 91% (397/437) and usual-type adenocarcinoma's PD-L1 positivity rate being 60% (35/58). In addition, the PD-L1 positivity rate varied depending on site of the specimen with 89.1% (261/293) positivity rate observed in cervix specimens compared to 25% (2/8) in brain metastases specimens. No significant difference in tumor mutational burden (TMB), microsatellite instability, and CD274 (encoding PD-L1) amplification was observed between PD-L1^positive and PD-L1^negative CXC subsets. By combining TMB with PD-L1, an additional 17 patients are eligible for pembrolizumab when compared to PD-L1 testing alone. TERT promoter alterations and APOBEC mutational signature were enriched in the PD-L1^positive CXC SCC (p = 0.011, and p = 0.004, respectively). Our study reveals important prevalence data on PD-L1 positivity in CXC non-SCC and suggests that further studies in these histologic subtypes are warranted. In addition, we also provide a key framework to guide both specimen selection and future investigations of predictors of immunotherapy response in cervical cancer patients. Lastly, TERT promoter alterations and APOBEC mutational signature may be a biologically unique subset of PD-L1^positive CXC SCC.