Clinical data were available for 293 pts; the most common cancers were colorectal (14.7%), non-small cell lung (13.7%), cholangiocarcinoma (13.3%) and melanoma (10.2%)...104 (35.8%) of 293 pts with POLE mutations received PD-1/L1 inhibitors as monotherapy or in combination...93 (88.4%) of 104 pts were evaluable for response: Radiological CR 4.3% (n = 4), PR 26.9% (n = 25), SD 22.6% (n = 21), PD 46.2% (n = 43), for a clinical benefit rate (CR + PR + SD) of 53.8%. Pathogenic status of POLE mutation was associated with clinical benefit to PD-1/L1 inhibitors (p = 0.04).