Current issues of ACP Journal Club are published in Annals of Internal Medicine


Etiology

First-degree relatives of patients with adenomas had an increased risk for colorectal cancer

ACP J Club. 1998 Nov-Dec; 129:75. doi:10.7326/ACPJC-1998-129-3-075


Source Citation

Ahsan H, Neugut AI, Garbowski GC, et al. Family history of colorectal adenomatous polyps and increased risk for colorectal cancer. Ann Intern Med. 1998 Jun 1;128:900-5.


Abstract

Question

Are first-degree relatives of patients with colorectal ademonatous polyps at increased risk for colorectal cancer?

Design

Reconstructed cohort study.

Setting

3 large colonoscopy practices in New York City, New York, United States.

Participants

Study and control participants were recruited from April 1986 to March 1988. 1554 first-degree relatives of 244 patients with adenomas (57% men, 90% white) formed the study group, and 2173 first-degree relatives of 362 adults (58% women, 84% white) with normal results on colonoscopy formed the control group. Inclusion criteria for the study group were age 35 to 84 years, local residence, and colonoscopic examination to at least the splenic flexure. Exclusion criteria were cancer, familial polyposis coli, inflammatory bowel disease, or initial colonoscopy done solely because of a family history of colorectal cancer.

Assessment of risk factors

Age, race, and type of relationship (sibling, parent, or child) of family members and age of persons who had had colonoscopy.

Main outcome measures

A history of colorectal or other cancer in first-degree relatives was ascertained by an interviewer who was blinded to the adenoma status of the relatives. The relative risk for colorectal cancer was set at 1.0 for relatives of persons with normal results on colonoscopy.

Main results

Patients with adenomas were more likely to be men, older, and white and were less likely to have had colonoscopy done for gastrointestinal symptoms than persons without adenomas. The prevalence of colorectal cancer in family members of patients with adenomas was 3.0%; in family members of persons without adenomas, prevalence was 4.7%. First-degree relatives and parents of patients with adenomas had anincreased risk for colorectal cancer; siblings showed only a trend towardincreased risk (Table). The risk for colorectal cancer increased with decreasing age of the patients with adenomas (Table). Persons with relatives who had adenomas did not have an increased risk for other types of cancer.

Conclusion

First-degree relatives of patients with colorectal adenomatous polyps had an increased risk for colorectal cancer.

Source of funding: In part, National Cancer Institute.

For correspondence: Dr. A.I. Neugut, Division of Oncology, Columbia-Presbyterian Medical Center, 630 West 168th Street, New York, NY 10032, USA. FAX 212-305-9413.


Table. Risk for colorectal cancer in relatives of patients with newly diagnosed adenomas confirmed by colonoscopy

Population Age at diagnosis Relative risk (95% CI)
First-degree relatives Any age 1.74 (1.24 to 2.45)
Parents Any age 1.58 (1.07 to 2.34)
Siblings Any age 1.58 (0.81 to 3.08)*
First-degree relatives ≤ 50 y 4.36 (2.24 to 8.51)

*Not significant.


Commentary

Screening for colorectal cancer has been shown to decrease mortality. Because screening that is targeted at high-risk persons is more cost-effective, identifying risk factors for disease has raised considerable interest. Ahsan and colleagues provide confirmatory evidence that persons who have a first-degree relative with a colorectal adenoma are at increased risk for cancer, particularly when the adenoma develops before age 50.

The findings make sense. Several genes have been identified that increase susceptibility to cancer and adenomas. Family members of patients with adenomas undoubtedly share these genes along with lifestyle and dietary factors that are associated with colorectal neoplasia.

It may be difficult to directly translate the study results into action. Although theauthors present data to suggest that colorectal cancer in family members can be reported accurately, it is doubtful that adenomas in relatives can be reported with similar fidelity. The most appropriate screening strategy for family members of patients with adenomas is also uncertain. Published guidelines provide some latitude in choosing from fecal occult blood testing to flexible sigmoidoscopy plus barium enema.Finally, it is important to put the findings in perspective. The relative increase in risk was modest, about 74%.

Based on the results of this and similar studies, we should be diligent about ascertaining whether first-degree relatives have a history of colorectal neoplasia—both cancer and adenomas. Individuals at higher-than-average risk by virtue of a positive family history should be strongly encouraged to be screened in some manner. Physicians who detect adenomas should probably suggest that their patients inform their first-degree relatives.

Robert S. Sandler, MD, MPH
University of North CarolinaChapel Hill, North Carolina, USA