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Microsatellite instability in the management of colorectal cancer
1Gastrointestinal Unit, Massachusetts General Hospital, 50 Blossom Street, Boston, MA 02114, USA.
Abstract:
Microsatellite instability (MSI) is a form of genetic instability caused by alterations in the DNA mismatch repair system. Approximately 15% of colorectal cancers display MSI due to a germline mutation in one of the mismatch repair genes (MLH1, MSH2, MSH6 and PMS2) or to epigenetic silencing of MLH1. Colorectal cancers with MSI have distinctive features, including a tendency to arise in the proximal colon, poor differentiation, lymphocytic infiltration and mucinous or signet-ring histology. Patients with MSI tumors appear to have a better prognosis than those with microsatellite stable tumors, but curiously the responses to 5-fluorouracil-based chemotherapy regimens are poorer with MSI tumors. Preliminary data suggest possible advantages of irinotecan-based regimens, but these findings need validation in well-designed clinical trials.
Insights
Microsatellite instability (MSI), a DNA repair defect, affects 15% of colorectal cancers. MSI tumors have unique features and a better prognosis but respond poorly to 5-FU chemotherapy.
Area of Science:
- Oncology
- Genetics
- Molecular Biology
Background:
- Microsatellite instability (MSI) arises from DNA mismatch repair system alterations.
- Approximately 15% of colorectal cancers exhibit MSI, often due to germline mutations or MLH1 silencing.
- MSI colorectal cancers present distinct characteristics like proximal location, poor differentiation, and specific histology.
Purpose of the Study:
- To summarize the key features of MSI in colorectal cancer.
- To discuss the prognostic implications of MSI.
- To review treatment response in MSI colorectal tumors.
Main Methods:
- Literature review of MSI in colorectal cancer.
- Analysis of clinical and pathological features associated with MSI.
- Evaluation of treatment outcomes based on MSI status.
Main Results:
- MSI tumors are associated with a better overall prognosis compared to microsatellite-stable tumors.
- Patients with MSI colorectal cancer show poorer response to 5-fluorouracil-based chemotherapy.
- Irinotecan-based regimens may offer advantages, requiring further clinical validation.
Conclusions:
- MSI is a significant molecular subtype of colorectal cancer with distinct clinical behavior.
- Treatment strategies for MSI colorectal cancer may need to be individualized.
- Further research is crucial to optimize therapeutic approaches for MSI tumors.
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