MO1-12-1Clinical introduction of Microsatellite instability (MSI) test for the Solid Tumors at a single institute

Abstract Backgrounds Pembrolizumab is recently approved in Japan for the microsatellite instability-high (MSI-H) solid tumor patients (pts) diagnosed with Promega panel (FALCOTM). Pembrolizumab is the first anti-tumor agent based on the biomarker, regardless of tumor types. MSI test has been performed as the screening test for the diagnosis of Lynch syndrome. However, it is not so familiar for the clinicians treating non-colorectal cancer. It is necessary to establish the in-hospital workflow and share the information and problems beyond the clinical departments as soon as possible. Methods We discussed the issue on the MSI test at the existing multidisciplinary conference which was organized to standardize the management of the immune-related adverse events (irAEs). In addition, we collaborated with the departments of pathology, clinical examination, and clinical genetic oncology. We used the MSI test itself to an inspection company outside of the hospital. Results The first case started from January 4th and a total of 142 pts received MSI test until March 7th. The origin of tumors were as follow; colorectal (n = 59), pancreas (n = 27), stomach (n = 12), cervix, uterine body and hepatobiliary tract (n = 8),prostate (n = 6) and, ovary and esophageal (n = 3), breast (n = 2) and others (n = 6). Surgical specimens were available in 94 cases (66.2%) and biopsy in 48 cases (33.8%). The results were obtained for 107 pts at the cut-off date. Among them, additional blood testswere required in 4 pts (3.7%). Due to the severe DNA degradation, one case (0.9%) could not be analyzed. Median turnaround time for the test was 15 days. Five pts (colon, n = 3/endometrial, n = 2) were found to have MSI-H and 3 were administered pembrolizumab with appropriate genetic counseling support. Conclusions We succeeded to introduce MSI test smoothly using the framework of multidisciplinary team approach. These efforts would be considered to be the basis for handling of comprehensive cancer panel in clinical practice.