Last Updated: 2001-12-25 13:00:45 EST (Reuters Health)
WESTPORT, CT (Reuters Health) - Hereditary nonpolyposis colorectal cancer (HNPCC) makes up the largest portion of colorectal (CRC) adenocarcinomas, according to a report in the December 1st issue of the International Journal of Cancer.
Drs. Kari Hemminki and Xinjun Li, from the Karolinska Institute, Hudding, Sweden, examined the risk of CRC adenocarcinoma in first-degree relatives by family history using data from the nation-wide Swedish Family-Cancer Database covering 9.8 million people.
The investigators calculated standardized incidence ratios (SIRs) based on gender-, age, period-, and tumor type specific rates. They recorded a total of 4794 CRCs in offspring and 67,925 CRCs in parents. "This is the largest study published on familial CRC and the only one reporting specifically on adenocarcinoma," Dr. Hemminki and Li note.
"For colon and rectal adenocarcinoma, the SIRs in offspring were 2.28 and 1.68 by parental CRC adenocarcinoma, giving attributable proportions of 6.45% and 3.31%, respectively," the team notes.
When both offspring and parents were diagnosed at a young age, the SIR of CRC was over 10. When two or more children had CRC, the risk for parents was over 100. When a parent had CRC, the risk for siblings was very high.
"The familial cancer sites that associated with CRC were those typical of HNPCC," the authors explain. They calculate that some 50% of familial colorectal adenocarcinomas are due to HNPCC, "and the proportion could be even higher among those diagnosed before age 40."
Int J Cancer 2001;94:743-748.
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