MO37-2 Retrospective Study of the Efficacy and Safety of Pembrolizumab for Solid Tumors with MSI-High

The results of KEYNOTE-164 and 158 show the efficacy of Pembrolizumab for MSI-High solid tumors. However, the frequency of MSI-High is low, so real-world data is still inadequate. Therefore, we investigated the frequency of MSI-High solid tumors in our hospital and examined the efficacy and safety of Pembrolizumab for unresectable cases. We retrospectively analyzed the patients with MSI-High solid tumors who received Pembrolizumab therapy between March 2019 and June 2021 in our hospital. MSI testing was performed on 331 patients with solid tumors, 23 of whom were MSI-High (6.9%). Only 9 of them were treated with Pembrolizumab. The patient background was 4 males and 5 females, with a median age of 70 years. The types of cancer were colorectal cancer (3 cases), gastric cancer (3 cases), biliary tract cancer (1 case), small intestine cancer (1 case), endometrial cancer (1 case). 5 cases with poor PS and 5 cases with peritoneal metastasis were included. the median PFS was 4.4 months (2-year PFS rate 33.9%), the median OS was not reached (2-year OS rate 63.5%), and the response rate was 33.3%. The immune-related Adverse Event was only 1 case of grade3 diarrhea. As previously reported, Pembrolizumab therapy for MSI-High solid tumors in our hospital was effective and tolerable in toxicity.