Abstract 101P
Background
Data on the prevalence of microsatellite instability-high (MSI-H)/deficient mismatch repair (dMMR) across advanced solid tumors are limited in patients from Asia. The clinicopathologic characteristics and treatment patterns in Asian patients with MSI-H/dMMR tumors are also not well known. We report the prevalence of MSI-H/dMMR across 6 tumor types in Asia and describe the clinicopathologic characteristics and treatment patterns for patients with MSI-H/dMMR and non–MSI-H/dMMR tumors.
Methods
Patients with advanced solid tumors (stage III/IV), regardless of prior therapy, from 29 study sites in Asia were included in this analysis. Biomarker testing was performed on archival tissue samples using the Ventana MMR IHC panel in patients from Asia-Pacific outside of Japan. Retrospective data on MSI-H PCR status using MSI-IVD Kit (FALCO) were collected in patients from Japan.
Results
A total of 1970 patients had samples evaluable for MSI-H/dMMR status in this analysis; 980 (49.7%) had gastrointestinal (GI) tumors (209 biliary tract; 285 gastric; 486 pancreatic) and 990 (50.3%) had gynecologic (GYN) tumors (190 cervical; 282 endometrial; 518 ovarian). The prevalence of MSI-H/dMMR was 5.4% (106/1970) overall, 2.8% (27/980) in GI tumors, and 8.0% (79/990) in GYN tumors. Prevalence of MSI-H/dMMR by regional cohort and tumor type is reported in the table. In the MSI-H/dMMR population, most patients had ECOG PS ≤1 (92.4%) and had undergone surgery (74.5%) and/or received chemotherapy (95.3%). Notably, a greater proportion of patients with MSI-H/dMMR tumors (34.0%) received treatment with immune checkpoint inhibitors (ICIs) as compared with patients with non–MSI-H/pMMR tumors (7.2%); 77.8% of the MSI-H/dMMR population who received ICIs were treated in the second-line or later setting. Table: 101P
Prevalence of MSI-H/dMMR by regional cohorts and tumor type
| % (n/N) | Biliary tract | Gastric | Pancreatic | Cervical | Endometrial | Ovarian |
| Japan cohort (MSI-IVD Kit [FALCO]) | 4.1 (4/98) | 4.2 (4/96) | 0.4 (2/486) | 1.7 (2/115) | 21.7 (33/152) | 2.3 (3/128) |
| Asia-Pacific cohort (Ventana MMR IHC panel) | 2.7 (3/111) | 7.4 (14/189) | N/A | 4.0 (3/75) | 14.6 (19/130) | 4.9 (19/390) |
| Overall cohort | 3.3 (7/209) | 6.3 (18/285) | 0.4 (2/486) | 2.6 (5/190) | 18.4 (52/282) | 4.2 (22/518) |
Conclusions
The prevalence of MSI-H/dMMR reported across 6 different tumor types in Asian patients was consistent with that reported in literature for non-Asian patients.
Clinical trial identification
Editorial acknowledgement
Medical writing and/or editorial assistance was provided by Holly C. Cappelli, PhD, CMPP, of ApotheCom (Yardley, PA, USA). This assistance was funded by Merck Sharp & Dohme LLC, a subsidiary of Merck & Co., Inc., Rahway, NJ, USA.
Legal entity responsible for the study
MSD Singapore.
Funding
Funding for this research was provided by MSD Singapore.
Disclosure
D.S. Tan: Financial Interests, Personal, Other, Consultancy Fees: AstraZeneca, Roche, MSD, Merck Serono, Bayer, Eisai; Financial Interests, Institutional, Research Grant: AstraZeneca, Bayer, Roche, Karyopharm; Financial Interests, Personal, Stocks/Shares: Asian Microbiome Library (AMiLi); Financial Interests, Personal and Institutional, Funding: Singapore Ministry of Health’s National Medical Research Council Clinician Scientist Award and Pangestu Family Foundation Gynaecological Cancer Research Fund. Y.M. Kim: Financial Interests, Institutional, Research Grant: MSD, AstraZeneca, Roche, Regeneron, Clovis Oncology. M. Kanai: Financial Interests, Personal, Stocks/Shares: Therabiopharma. Inc.; Financial Interests, Personal, Advisory Role: Therabiopharma. Inc.; Financial Interests, Personal, Speaker’s Bureau: Chugai Pharmaceutical Co., Ltd.; Financial Interests, Institutional, Research Grant: Molecular Health. S.Y. Rha: Other, Personal, Advisory Role: Amgen, Daiichi Sankyo, BMS, Indivumed, Merck, Beigene, Eisai. R. Ramar: Financial Interests, Personal, Full or part-time Employment: MSD International GmbH; Financial Interests, Personal, Stocks/Shares: MSD International GmbH. M.T. Wong: Financial Interests, Personal, Full or part-time Employment: MSD International GmbH; Financial Interests, Personal, Stocks/Shares: MSD International GmbH. All other authors have declared no conflicts of interest.