Clinicopathological and molecular biological features of colorectal cancer in patients less than 40 years of age

Background: The aim of the present study was to identify the clinicopathological and molecular biological characteristics of early-onset colorectal cancers. Methods: The clinicopathological and molecular biological parameters of 138 consecutive patients with colorectal cancer aged less than 40 years were compared with those of 339 patients aged 60 years or more. Results: The younger patients with colorectal cancer had more mucin-producing (14.5 versus 4.7 per cent; P < 0.001) and poorly differentiated (7.2 versus 3.3 per cent; P = 0.015) tumours, a higher incidence of synchronous (5.8 versus 1.2 per cent; P = 0.007) and metachronous (4.0 versus 0.6 per cent; P = 0.023) colorectal cancers, and more advanced tumour stage (P < 0.001) than older patients. The operative mortality rate was lower (0.7 versus 5.0 per cent; P = 0.026), and cancer-specific survival was similar (in stage I, II and III disease; P > 0.05) or better (in stage IV disease; 95 per cent confidence interval 22.50 to 28.41 versus 12.61 to 17.05 months; P < 0.001). There was a higher percentage of normal p53 expression (61.1 versus 46.8 percent; P = 0.023) and high-frequency microsatellite instability (MSI-H) (29.4 versus 6.3 per cent; P < 0.001), and a similar family history of cancer (17.5 versus 14.2 per cent; P > 0.05), compared with older patients. Conclusion: Young patients with colorectal. cancer have several distinct clinicopathological and molecular biological features. The mechanisms underlying the inconsistency between the presence of MSI-H and a family history of cancer in these early-onset colorectal cancers deserve further investigation.