Mutually exclusive expression of CD73 and PDL1 in tumors from patients (pt) with NSCLC, gastroesophageal (GE) and urothelial bladder carcinoma (UBC).

3079Background: Tumors use multiple means of immune evasion, notably the programmed death-1 (PD1)/PDL1 pathway. Anti-PD1/PDL1 therapy induces anti-tumor activity and has improved pt outcomes. Activation of the immunosuppressive CD39/CD73/adenosine pathway might play a role in pts who do not benefit from anti-PD1/PDL1 therapies. We evaluated expression of CD73 and PDL1 and explored the association between CD73 and intraepithelial (IE) CD8+ cells (TILs) to begin to understand their potential interplay in cancer. Methods: Immunohistochemistry for PDL1, CD73 and CD8 was conducted on tumors of non-squamous NSCLC (NSq) (n=42), GE (n=50), and UBC (n=50). PDL1 and CD73 were scored by image analysis with Definiens software. IE CD8+ TILs were scored semi-quantitatively by a pathologist (0-2 = low; 3-4 = high). Using the top tertile of PDL1 and CD73 for high expression levels, a Fisher’s meta-analysis was calculated across the three indications. Results: Across all tumors, 25% (35/142) were PDL1 high (+), but CD73 l...