A population-based study of age-related variation in clinicopathological features, molecular. Markers and outcome from colorectal cancer.

Background: To investigate age-related differences in clinicopathological features, molecular alterations and patient survival in a large, population-based series of CRC. Patients and Methods: The study cohort consisted of 5,971 cases diagnosed between 1993 and 2003 representing over 90% of the CRCs diagnosed in the state of Western Australia. Results: Patients aged ≤30, ≤40, ≤50 and ≤60 years comprised 0.9%, 3.1%, 10.6% and 27.8% of all cases, respectively. The proportion of rectal cancers and tumors with poor differentiation was higher in ≤30-year-old patients and decreased progressively with age. The incidence of tumors with microsatellite instability was significantly higher in patients aged ≤40 years (18.3%) compared to those aged 41-60 years (6.6%; p<0.0001). TP53 mutations were also more frequent (p=0.002), however K-ras mutations were less common (p=0.0001) when comparing the same age groups. Conclusion: These results provide evidence for major age-related differences in the clinical and molecular features of CRC.