Family History of Colorectal Cancer Is Not Associated with Colorectal Cancer Survival Regardless of Microsatellite Instability Status

BACKGROUND: Individuals with a family history of colorectal cancer in first-degree relatives have an elevated risk of developing colorectal cancer themselves, particularly colorectal cancer exhibiting high microsatellite instability (MSI-high). Given that MSI-high colorectal cancer is associated with a favorable prognosis, it is plausible that having a family history of colorectal cancer could, in turn, be favorably associated with colorectal cancer survival. METHODS: This study comprised N = 4,284 incident colorectal cancer cases enrolled in the Colon Cancer Family Registry via population-based cancer registries. Using Cox proportional hazards regression, we evaluated the association between family history and both overall and disease-specific survival, accounting for MSI status and tumor site via stratified analyses and statistical adjustment. RESULTS: There was no evidence of association between family history and overall [hazard ratio (HR), 0.92; 95% confidence interval (CI), 0.79-1.08] or disease-specific survival (HR, 1.03; 95% CI, 0.85-1.24) for all cases combined, after adjustment for MSI status or tumor site. Only for rectal cancer cases was colorectal cancer family history modestly associated with more favorable overall survival (HR, 0.75; 95% CI, 0.56-0.99). CONCLUSIONS: Although individuals with a family history of colorectal cancer were more likely to have MSI-high tumors than those with nonfamilial disease, this did not translate to a survival benefit. IMPACT: Overall, there is no evidence that family history of colorectal cancer is associated with colorectal cancer survival; however, specific mechanisms underlying family history may have prognostic impact and merit further study.