201P - Immunotherapy in advanced mismatch repair deficiency endometrial cancer: A real-world single center experience

Background

Mismatch repair (MMR) deficiency is seen in 15-30% of patients with endometrial cancer (EC). Single agent immune checkpoint inhibitors (ICI) have been approved for treatment with advanced endometrial cancer based on the high response rates and the long duration of response. There is very limited data of MMR deficient EC patients treated with ICI from India.

Methods

This is a single center, retrospective study of patients with MMR deficiency EC who received ICI. The endpoints were objective response rate (ORR), progression free survival (PFS), overall survival (OS) and adverse event (AE) profile.

Results

47 advanced EC patients were tested for MMR deficiency by immunohistochemistry (IHC) between June 2019 to Jan 2022. 12 patients (25.5%) were found to have MMR deficiency. 10 patients of advanced EC with MMR deficiency were treated with ICI. Median age was 59 years (52-76 years). MLH1/ PMS2 loss was seen in 8 patients, while 2 patients had MSH2/ MSH6 loss. 9 patients had received first line treatment with carboplatin + paclitaxel, and had progressed. Nivolumab was given in 8 patients and pembrolizumab in 2 patients. 1 patient was treated in the first line, while 9 in the second line. The number of ICI cycles ranged from 4-26. 2 patients (20%) achieved a complete response (CR), 4 (40%) partial response, 4 (40%) had progression, and the ORR was 60%. The median PFS was 8 months (2-17 months) and the median OS was not reached. The 1 year OS rate was 56%. The median duration of response was 16 months. The common side effects were hypothyroidism in 3 (30%) and skin rashes in 2 (20%) patients, with no grade 3/4 AEs.

Conclusions

MMR deficient EC is not uncommon, and were seen in 25.5% of our patients. MMR testing by IHC is an easy, quick and cost effective test for picking up this population. ICI with nivolumab or pembrolizumab showed a high ORR and durable response in our patients. It is imperative that we check every advanced EC for MMR deficiency, as this patient population 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, Invited Speaker: AstraZeneca, Eisai, Novartis; Financial Interests, Personal, Advisory Role: BMS, Eli Lilly, Merck, MSD, Pfizer, Roche, Cipla. All other authors have declared no conflicts of interest.