Association between microsatellite status and characteristics and outcomes of early-onset compared to late-onset...

Area of Science:

• Oncology
• Gastroenterology
• Genetics

Background:

• Microsatellite instability (MSI) is a key prognostic factor in colorectal cancer (CRC).
• Understanding MSI's role in early-onset versus late-onset rectal cancer is crucial for tailored treatment strategies.

Purpose of the Study:

• To investigate the influence of MSI status on the clinical characteristics and outcomes of early-onset (<50 years) compared to late-onset rectal cancer.
• To evaluate differences in presentation, treatment, and survival based on MSI status across age groups.

Main Methods:

• Retrospective cohort study utilizing the US National Cancer Database (2004-2019).
• Analysis of baseline characteristics, treatment patterns, short-term outcomes, and overall survival (OS) in 48,407 rectal cancer patients.
• Comparison of early-onset (<50 years) and late-onset patient groups stratified by MSI status (MSI-H vs. MSS).

Main Results:

• MSI-high (MSI-H) tumors were more frequent in early-onset rectal cancer patients and associated with less advanced stage IV disease and liver metastasis.
• In both age groups, MSI-H tumors showed higher rates of pT3-4 stage, mucinous histology, and poor differentiation compared to microsatellite-stable (MSS) tumors.
• No significant difference in median overall survival was observed between MSI-H and MSS tumors in either early-onset or late-onset groups.

Conclusions:

• MSI-H rectal cancers, particularly in early-onset cases, present with distinct characteristics including less frequent distant metastases.
• While MSI status influences tumor morphology and stage, it does not appear to be a significant predictor of overall survival in rectal cancer across different age groups.
• Further research may explore targeted therapies for MSI-H rectal cancers based on age-specific presentations.