Colorectal Cancer Coverage from Every Angle
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Differences in Mismatch Repair Genes in Primary Colorectal Cancer and Metastases

By: Lauren Harrison, MS
Posted: Wednesday, January 8, 2020

Concordance of microsatellite instability and mismatch repair status between primary and metastatic lesions is likely to be organ-specific in colorectal cancer. Metastases in the liver, lung, and lymph nodes seem to show high concordance with primary tumors, whereas metastasis to the ovaries or peritoneum seem to show more discrepancy. This work was published in the Journal of the National Comprehensive Cancer Network by Wen-Zhuo He, MD, of Sun Yat-sen University Cancer Center, China, and colleagues.

A total of 369 patients diagnosed with metastatic colorectal cancer who were diagnosed between January 2008 and December 2016 were included in the study. Patients had both primary and metastatic tumors, which were evaluated for mismatch repair status and microsatellite instability. Immunohistochemistry and polymerase chain reaction assays were performed on all samples. There were 48 patients with defective mismatch repair and 321 with proficient mismatch repair.

A total of 46 patients had high microsatellite-instable primary tumors, and of these patients, 80.4% had high microsatellite-instable metastatic tumors as well. This group of patients had metastases in the perineum (43.5%), the liver (21.7%), distant lymph nodes (19.6%), ovaries (8.4%), and lungs (6.5%). High concordance was noted in patients whose metastases were present in the liver, lungs, or distant lymph nodes. Discrepancy was more likely to be found in peritoneal or ovarian metastasis. In these cancers, there was a change from high-microsatellite instability in the primary cancer to microsatellite stability in the metastatic cancer. There was also less lymphocyte infiltration in these cases. These changes did not seem to impact survival, as the median overall survival of patients with high microsatellite-instability and microsatellite-stable tumors was 21.3 and 21.6 months (P = .774). Patients with proficient mismatch repair tumors had a discrepancy rate of 1.6%.

Disclosure: For full disclosures of the study authors, visit jnccn.org.



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