© 2001 by Oxford University Press
Journal of the National Cancer Institute, Vol. 93, No. 8, 651,
April 18, 2001
© 2001 Oxford University Press
CORRESPONDENCE |
Re: Characterization of Hereditary Nonpolyposis Colorectal Cancer Families From a Population-Based Series of Cases
Correspondence to: Kari Hemminki, M.D., Ph.D., Department of Biosciences, Karolinska Institute, Novum, 141 57 Huddinge, Sweden (e-mail: kari.hemminki{at}cnt.ki.se).
For cancer prevention and research, it is important to have accurate knowledge of the frequency of specific syndromes. Population-based studies can be valuable tools in obtaining such data because they avoid selection bias. The study by Peel et al. (1) was a welcome attempt to quantify the proportion of hereditary nonpolyposis colorectal cancer (HNPCC) on the basis of the Amsterdam criteria. These criteria require that at least three family members be ascertained with colorectal cancer and that one of these patients be a first-degree relative of the other two (i.e., an affected parent and two affected offspring, two affected siblings and one with an affected offspring, or three affected generations). The criteria have been criticized because they depend on family size (2). If the average family size is shrinking in a population, the apparent proportion of so-defined HNPCC is bound to become smaller (2). Nuclear families with three or more affected individuals are rare in current Western populations. For example, the Swedish Family-Cancer Database with 2.1 million nuclear families contains only some 20 families (0.001%), where one parent and two or more offspring present with colorectal cancer (3). This implies that most HNPCC families fulfilling the Amsterdam criteria depend on second-degree relations. If grandparents are included then, on average, colorectal cancers in these families are diagnosed in the course of some 50 or more years— e.g., a grandchild in the 1990s, a child in the 1960s, and a parent in the 1930s. The major problem is how the HNPCC-related cancers from the early part of the last century are ascertained.
Glanz et al. (4) carried out a questionnaire study of familial colorectal cancer in Hawaii, asking probands to identify colorectal cancers among the first-degree relatives. Despite a medically confirmed diagnosis, 25% of the probands failed to report colorectal cancer in offspring or siblings. Such false reporting of cancers in family members is known from other studies as well [see (4)]. Any false reporting has severe consequences for the application of the Amsterdam criteria. If the reporting of cancer in one sibling is correct with the probability of 0.75, then the probability of having two first-degree relatives correctly reported is 0.56. Moreover, underreporting is not the only problem; false-positive reporting is also likely (5). No doubt, reporting of cancers from a second-degree relative is even worse, and most families fulfilling the Amsterdam criteria include such relations. It is likely that the reporting is more accurate in a clinical study, where the patient has had many visits and is often assisted by a relative. The study by Peel et al. (1) was carried out as a telephone interview, and the report gives no indication whether any measures were taken to confirm the reported cases of colorectal cancer in the families, particularly among second-degree relatives. Unless some confirmation is available, the figures on the population proportion of HNPCC and the apparently high proportion of proximal cancers remain speculative.
REFERENCES
1
Peel DJ, Ziogas A, Fox E, Gildea M, Laham B, Clements E, et al. Characterization of hereditary nonpolyposis colorectal cancer families from a population-based series of cases. J Natl Cancer Inst 2000;92:1517–22.
2
Potter JD. Colorectal cancer: molecules and populations. J Natl Cancer Inst 1999;91:916–32.
3 Dong C, Hemminki K. Modification of cancer risks in offspring by sibling and parental cancers from 2,112,616 nuclear families. Int J Cancer. In press 2001.
4
Glanz K, Grove J, Le Marchand L, Gotay C. Underreporting of family history of colon cancer: correlates and implications. Cancer Epidemiol Biomarkers Prev 1999;8:635–9.
5 Gibbs M, Stanford JL, McIndoe RA, Jarvik GP, Kolb S, Goode EL, et al. Evidence for a rare prostate cancer-susceptibility locus at chromosome 1p36. Am J Hum Genet 1999;64:776–87.[CrossRef][Web of Science][Medline]cancerlit;99162200
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