Programmed cell death ligand 1 (PD-L1) expression landscape and its relationship with tumor mutational burden (TMB) in a community-based cancer center patient population in rural central Nebraska.

Abstract

e15141 Background: PD-L1 and TMB are the most widely used immunotherapy biomarkers to identify populations who would benefit from immunotherapy, with the higher values predicting better therapeutic efficacy. We sought to explore the occurrence and correlation of these two biomarkers in a community based cancer center patient population in rural central Nebraska. Methods: One hundred sixty consecutive cancer patients(pts) diagnosed and treated between 2018-2022 at Morrison Cancer Center were evaluated. Malignant tumor tissue specimens were analyzed for PD-L1expression and TMB (Foundation test). PD-L1 expression was classified as low ( < 1%), intermediate (1% ≥ PD-L1 < 50%), high (≥ 50%), and TMB classified as low [1–5 mutations/Megabase (muts/Mb)], intermediate (6–19 muts/Mb), high (≥ 20 muts/Mb)]. PD-L1 and TMB values were treated as continuous variables to calculate a Pearson correlation coefficient and p value. Results: Mean age at diagnosis was 64 years (range 33-89). Malignant histology diagnoses included 55 pts with lung, 18 colorectal, 12 breast, 15 unknown primary, 15 pancreas, 10 renal, 3 melanoma, 1 thyroid, 6 ovary, 5 uterus, 5 head and neck, 5 prostate, 5 biliary, and 1 vulvar. Fifty four percent (86/160) of pts had low, 33% (53/160) had intermediate, and 13% (21/160) had high PD-L1 expression score with a mean PD-L1 value of 13.8% (range 0-100). Sixty six percent (106/160) of pts had low, 30% (48/160) had intermediate, and 4% had high TMB with a mean TMB value of 5.6 muts/Mb (range 0-66). A marginal linear correlation between PD-L1 expression and TMB was observed (Pearson Correlation Coefficient = 0.172, P = 0.0270). Conclusions: PD-L1 and TMB are both important biomarkers for immunotherapy. Increasing availability and use of both PD-L1 and TMB testing in the community oncology practice beseeches the question of frequency of these two biomarkers in various cancers in the community oncology patient population as well as any association between them. The results of our study gives a glimpse of the distribution landscape of these two biomarkers for community oncology patients and suggest that PD-L1 and TMB may be independent markers with a weak association. PD-L1 and TMB may each inform use of immunotherapy by different mechanisms. [Table: see text]