Prognosis and chemosensitivity of non-colorectal alimentary tract cancers with microsatellite instability.

Background: Data on outcomes of microsatellite instable and/or mismatch repair deficient (dMMR/MSI) digestive non-colorectal tumors are limited.

Aims: To evaluate overall survival (OS) of patients with dMMR/MSI digestive non-colorectal tumor.

Methods: All consecutive patients with a dMMR/MSI digestive non-colorectal tumor were included in this French retrospective multicenter study.

Results: One hundred and sixteen patients were included with a mean age of 63.6 years and 32.6% with a Lynch syndrome. Most tumors were oesophago-gastric (54.3%) or small bowel (32.8%) adenocarcinomas and at a localized stage at diagnosis (86.7%). In patients with localized tumors and R0 resection, median OS was 134.0 ± 64.2 months. Median disease-free survival (DFS) was 100.3 ± 65.7 months. Considering oesophago-gastric tumors, median DFS was improved when chemotherapy was added to surgery (not reached versus 22.8 ± 10.0 months, p = 0.03). In patients with advanced tumors treated by chemotherapy, median OS was 14.2 ± 1.9 months and median progression-free survival was 7.4 ± 1.6 months.

Conclusion: dMMR/MSI digestive non-colorectal tumors are mostly diagnosed at a non-metastatic stage with a good prognosis. Advanced dMMR/MSI digestive non-colorectal tumors have a poor prognosis with standard chemotherapy.