Young patients with colorectal cancer are genetically susceptible
Researchers are advocating genetic testing for young patients with early onset colorectal cancer, after discovering mutations that predispose to the disease, as in hereditary non-polyposis colorectal cancer (HNPCC). Testing should be done even if family histories do not conform to the Amsterdam criteria for HNPCC, they say.
High frequency microsatellite instability was evident in eight tumours from 11 patients (73%) evaluated in cohort of 16 patients aged ≤24 years at diagnosis. Germline mutations occurred in mismatch repair genes in six out of 14 tumours (43%) from 14 patients tested—two mutations in MLH1, three in MSH2, and one in PMS2. Half the families met the Amsterdam criteria for HNPCC. Among the others, four out of five patiants tested had tumours with high frequency microsatellite instability and germline mutations were present in three. Secondary tumours occurred in seven (44%) patients in the entire cohort during follow up, three quarters in the gastrointestinal tract; and in almost three quarters the primary tumour showed high frequency microsatellite instability.
The cohort was identified from 1382 patients in the Familial Gastrointestinal Cancer Registry, Toronto, Canada, 1960–2003. Clinical and pathological reports were reviewed and pedigrees drawn up from clinical data and interviews with the probands and their relatives. DNA was extracted from microdissected material from paraffin blocks of the original resected tumours to look for HNPCC-type mutations.
Case series of colorectal cancer in children and adolescents have not focused on genetic profiles of the tumours or looked for genetic susceptibility within families before.
