Abstract 6276: Real-world prevalence of MSI/MMR testing for patients with recurrent or advanced endometrial cancer in Europe
Authors: Zhang Jingchuan , Kelkar Sneha S. , Prabhu Vimalanand S. , Corman Shelby , Qiao Lucy , Grall Véronique , Miles Nicola 
Published: June 2022

Abstract
Introduction: Microsatellite instability (MSI) due to defective DNA mismatch repair (MMR) has emerged as an actionable biomarker in endometrial cancer (EC) with the recent availability of MSI-directed therapies. Currently, there is no data on utilization of MSI/MMR testing for EC in Europe. This study aims to assess the real-world prevalence of MSI/MMR testing and related tumor status in women with recurrent or advanced EC (aEC) in Europe.
Methodology: Endometrial Cancer Health Outcomes-Europe (ECHO-EU) is a multicenter retrospective chart review study in United Kingdom (UK), Germany (GE), Italy (IT) and Spain (SP). Physicians extracted de-identified data from medical records of women (≥18 years) diagnosed with aEC, who progressed after prior systemic therapy between July 2016 and July 2019. Patients’ demographics, clinical characteristics, and MSI/MMR testing data were collected. Women were categorized by MSI/MMR status.
Results: Interim data from 81 physicians included 349 eligible women (UK=83, GE=64, IT=102, SP=100). More than 85% of physicians were medical oncologists and 91% had a hospital-based practice. At aEC diagnosis, eligible women were on average 68 years, 91% were Stage III/IV, and 56% had endometrioid carcinoma. Overall, 36% of patients were tested by either polymerase chain reaction (PCR) for MSI or immunohistochemistry (IHC) for MMR (UK=33%, GE=31%, IT=25%, SP=55%). Of those with ≥1 test, 54% were tested prior to systemic therapy initiation, with large inter-country differences (16-70%), 20% were MSI-high/deficient MMR (dMMR), 73% were non-MSI-high/proficient MMR (pMMR), and 7% had a mixed result. (Table)
Conclusion: Overall MSI/MMR testing rates in Europe are low. Approximately 1 in 5 tested patients had MSI-high/dMMR tumors and three quarters had non-MSI-high/pMMR tumors. Knowledge regarding MSI/MMR testing and related tumor status may be helpful for optimal utilization of targeted therapies for aEC patients in Europe.
Table - Patient characteristics and MSI/MMR testing/prevalence in women with aEC in Europe Variable All (N = 349) UK (N = 83) Germany (N = 64) Italy (N = 102) Spain (N = 100) Age at diagnosis of advanced or recurrent EC (years), Mean (SD) 67.5 (9.2) 69.0 (8.4) 68.5 (8.3) 66.1 (9.3) 67.1 (10.1) Stage III-IV at initial diagnosis, N (%) 318 (91.1) 78 (94) 58 (90.6) 96 (94.1) 86 (86) ECOG at recurrent or advanced diagnosis, N (%) 0-1 287 (82.2) 79 (95.2) 34 (53.1) 88 (86.3) 86 (86) Any MSI/MMR testing (IHC or PCR), N (%) Not tested 222 (63.6) 56 (67.5) 44 (68.8) 77 (75.5) 45 (45) Tested 127 (36.4) 27 (32.5) 20 (31.3) 25 (24.5) 55 (55) MSI/MMR status, N (%) MSI-High/dMMR 25 (19.7) 7 (25.9) 3 (15) 3 (12) 12 (21.8) Non-MSI-High/pMMR 93 (73.2) 20 (74.1) 14 (70) 19 (76) 40 (72.7) Mixed 9 (7.1) 0 (0) 3 (15) 3 (12) 3 (5.5) MSI/MMR testing administration, N (%) Before treatment initiation 68 (53.5) 19 (70.4) 10 (50) 4 (16) 35 (63.6)
Citation Format: Jingchuan Zhang, Sneha S. Kelkar, Vimalanand S. Prabhu, Shelby Corman, Lucy Qiao, Véronique Grall, Nicola Miles. Real-world prevalence of MSI/MMR testing for patients with recurrent or advanced endometrial cancer in Europe [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 6276.