Genetic counselling and testing
for susceptibility to breast, ovarian
and colon cancer: Where are we today?
David E.C. Cole, MD, PhD, FRCPC; Steve Gallinger, MD, MSc, FRCSC; David R. McCready, MD, FRCSC;
Barry Rosen, MD, FRCSC; June Engel, PhD; David Malkin, MD, FRCPC
Canadian Medical Association Journal 1996; 154: 149-155
From the departments of Clinical Biochemistry and Medicine, Surgery, Obstetrics and Gynecology, and Pediatrics, University of Toronto, Toronto, Ont. Ms. Engel is editor of Health News, Faculty of Medicine, University of Toronto.
This is the first in a series on genetic screening and counselling for heritable breast, ovarian and colon cancer. The second article [abstract] appears in the Feb. 15 issue and the third article [abstract] appears in the Mar. 15 issue.
Paper reprints of the full text may be obtained from: Dr. David E.C. Cole, Rm. 415, Department of Clinical Biochemistry, University of Toronto, 100 College St., Toronto ON M5G 1L5; davidec.cole@utoronto.ca
Abstract
Recent advances in our understanding of the genetic characteristics of cancer will change approaches to genetic screening and counselling. Cancer results from multiple, cumulative mutations in genes that regulate cell replication and differentiation. In familial cancer a germ-line mutation is passed on in an autosomal dominant pattern, but cancer will develop in people who inherit the defect only if other mutations also occur in susceptible somatic cells. The tumour-suppressor gene known as BRCA1 is thought to affect half of those families who have an inherited breast cancer syndrome and most families with a breast and ovarian cancer syndrome. Another gene, BRCA2, is thought to affect most of the remaining families with a breast-cancer-only syndrome. Hereditary nonpolyposis colon cancer (HNPCC) is caused by mutations in surveillance genes that protect DNA from the spontaneous errors that occur during cell division. Because there are no outcome data on which to base practice guidelines for genetic screening or management of asymptomatic carriers in families at risk, testing should be restricted to research settings.
CMAJ January 15, 1996 (vol 154, no 2)