TY - JOUR T1 - Molecular and Radiological Features of Microsatellite Stable Colorectal Cancer Cases With Dramatic Responses to Immunotherapy JF - Anticancer Research JO - Anticancer Res SP - 2985 LP - 2992 DO - 10.21873/anticanres.15080 VL - 41 IS - 6 AU - BRIDGET P. KEENAN AU - KATHERINE VAN LOON AU - ANURADHA D. KHILNANI AU - NICHOLAS FIDELMAN AU - SPENCER C. BEHR AU - CHLOE E. ATREYA AU - DAVID Y. OH Y1 - 2021/06/01 UR - http://ar.iiarjournals.org/content/41/6/2985.abstract N2 - Background/Aim: The majority of colorectal cancer (CRC) cases, which are microsatellite stable (MSS) and do not harbor mismatch repair deficiency/microsatellite instability, are resistant to immunotherapy. Identification of patients with exceptional responses in MSS CRC and predictive biomarkers is an unmet need that needs to be addressed. Case Report: We report three cases of MSS CRC with durable clinical benefit from immunotherapy with anti-PD-1 checkpoint inhibitors. Two cases bear a POLE P286R mutation, which has been associated with lack of immunotherapy response in MSS CRC. Two cases bear alterations in Ataxia-Telangiectasia Mutated (ATM) which may contribute to observed responses, including interaction with a co-administered intratumoral stimulator of interferon genes (STING) pathway agonist in one patient. Conclusion: Novel DNA damage repair alterations, including mutations in ATM, can provide insight into additional mechanisms by which genomic alterations can sensitize MSS CRC to diverse immunotherapies. ER -