Adherence to Microsatellite Instability Testing in Young-Onset Colorectal Cancer Patients.
BACKGROUND:: In 1997, the Bethesda guidelines recommended microsatellite instability testing for colorectal cancer in patients younger than 45 years to screen for Lynch syndrome. In 2004, these guidelines were revised to set the screening age at younger than 50 years. OBJECTIVE:: The aim of this study was to investigate to what extent these guidelines were followed in young patients with colorectal cancer in the Mid-Netherlands and to identify the predictors of nonadherence. DESIGN:: This is a retrospective cohort study. SETTINGS:: This study was conducted in 1 academic and 5 nonacademic hospitals. PATIENTS:: All patients diagnosed with colorectal cancer younger than 45 years in the period 1999 to 2004 and younger than 50 years in the period 2005 to 2008 were included. Patients known to be affected by or at risk for Lynch syndrome before diagnosis were excluded. MAIN OUTCOME MEASURES:: Patient and tumor characteristics, including microsatellite instability testing results, were collected from the database of the Comprehensive Cancer Center, the National Pathological Archive, participating hospitals, and the regional institute of clinical genetics. Logistic regression analysis was performed to detect a trend in adherence over the years and to identify the predictors of nonadherence. RESULTS:: A total of 335 patients were identified. Microsatellite instability testing was performed in 130/335 (39%) patients. Adherence did not improve in the period 1999 to 2008. We found that older age at diagnosis (OR 0.96, 95% CI 0.92-1.00), male sex (OR 0.60, 95% CI 0.38-0.95), and stage IV colorectal cancer (OR 0.45, 95% CI 0.24-0.84) were independent predictors of nonadherence, whereas proximal tumor localization, poor differentiation, and mucinous histology were not. LIMITATIONS:: This study was limited by its retrospective design. CONCLUSIONS:: Adherence to the Bethesda guidelines in young-onset colorectal cancer is low, particularly in older and male patients and in patients with metastatic disease, which suggests that efforts to improve adherence are needed.
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