Abstract 84P
Background
Metastatic cancers with mismatch repair (MMR) deficiency, seen especially in cancers of the uterus and gastrointestinal tract, are rare and seen in about 5% of patients. They show very good and durable response to treatment with immunotherapy, leading to a tumor agnostic approval in this indication. There is very limited data of MMR deficient patients treated with immunotherapy from India.
Methods
This is a single center, retrospective study of patients with metastatic mismatch repair (MMR) deficiency cancers who received immunotherapy. The endpoints were objective response rate (ORR), progression free survival (PFS) and overall survival (OS).
Results
Between Jan 2018 to Jan 2021, 166 metastatic cancer patients were tested for MMR deficiency by immunohistochemistry (IHC). The primary site was colon in 80, stomach in 54, uterus in 32 patients; and out of these, 4,6,7 patients respectively had MMR deficiency (17 patients=10.2%). 14 MMR deficient patients who had progressed on at least one line of chemotherapy received immunotherapy with either nivolumab or pembrolizumb. There were 7 males and 7 females. The median age was 58 years (37-81 years). 6 had carcinoma stomach, 6 had uterine cancer and 2 had colon cancer. 7 patients received immunotherapy as second line, 6 as third line and 1 as fourth line treatment. The number of immunotherapy cycles ranged from 2 to 50. 9 patients had a partial response, 1 had stable disease and 4 had progression by recist criteria. The ORR was 64%. The median PFS was 18 months (2-38 months) and median OS was 22 months. 4 patients have crossed 2 years without progression, and 2 patients have crossed 3 years without progression.
Conclusions
MMR deficient metastatic cancers are uncommon and are seen in 10% of patients in our study. MMR testing by IHC is an easy, quick and cost-effective test for picking up this population. Immunotherapy with nivolumab or pembrolizumab showed a high ORR and durable response in our patients. The median PFS of 18 months and median OS of 22 months was better than historical controls, inspite of immunotherapy being given in second line and beyond setting. It is imperative that we check every metastatic cancer for MMR deficiency, as this patient population, even though rare, has the potential to become long term survivors.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
Amit Rauthan.
Funding
Has not received any funding.
Disclosure
A. Rauthan: Financial Interests, Personal, Advisory Board: AstraZeneca; Financial Interests, Personal, Advisory Board: BMS; Financial Interests, Personal, Advisory Board: Eisai; Financial Interests, Personal, Advisory Board: Eli Lilly; Financial Interests, Personal, Advisory Board: Merck; Financial Interests, Personal, Advisory Board: MSD; Financial Interests, Personal, Invited Speaker: Novartis; Financial Interests, Personal, Invited Speaker: Pfizer; Financial Interests, Personal, Advisory Board: Roche; Financial Interests, Personal, Advisory Board: Cipla. All other authors have declared no conflicts of interest.