Family history of colorectal cancer as a marker of potential malignancy within a screening program

Abstract

Epidemiologic studies have shown that asymptomatic adult relatives of colorectal cancer patients are at increased risk for developing this tumor. A prospective, published pilot study confirmed this added risk and demonstrated the importance of the family history of cancer as a marker of potential malignancy. The study group was enlarged to include 471 asymptomatic adult, first degree relatives of patients having large bowel neoplasia (cancer or adenomatous polyps) but without polyposis syndromes. These first degree relatives were screened by fecal occult blood examinations and flexible sigmoidoscopy, followed by colonoscopy when indicated. Adenomatous polyps or cancer were found in 8.1% of the study group as compared with 3.7% in a comparison group of screens, not having the same family history of neoplasia and undergoing similar screening tests. Of the study group the age-adjusted rate for colorectal adenomas or cancer increased threefold (P less than 0.001) for subjects older than 40 years and an even higher fivefold relative risk was found for large bowel cancer only (P = 0.01). This was true even if there was only one relative with colorectal neoplasia (P less than 0.01) but was even more pronounced among those having more than one affected relative. The results confirm the usefulness of the family history, of even one member with large bowel neoplasia, in isolating a group at high risk for these lesions. This group would most likely benefit from regular cancer and adenomatous polyp screening particularly when older than 40 years.

Endoscopic screening of relatives of patients with colorectal cancer

“…In studies in which yield has been broken down by age, findings have been similar to our own, with the incidence of neoplasia rising from 0–4.3% under the age of 40 years to 16–32% over the age of 60 years 1315 18 21 Comparing yield with that found in the general population is important, particularly at lower levels of familial risk. Yield obtained with 60 cm flexible sigmoidoscopy was 5.7% in a population of mean age 55 years 27.…”

“…Yield obtained with 60 cm flexible sigmoidoscopy was 5.7% in a population of mean age 55 years 27. Although all controlled studies have shown a higher yield in family members than controls,9 18 21 25 even in one of the larger studies this has failed to reach statistical significance 21…”

“…Yield of adenomas in individuals with a single affected relative (1:17 risk) ranges from 5.3% (58% of adenomas being less than 5 mm in size)18 to 17% (8% larger than 1 cm in size) 9. An adenoma yield from flexible sigmoidoscopy of 19% has been reported 25.…”

“…Retrospective reports of colonoscopy give rates of polyp detection as diverse as 10.6 and 63% 1516 Adenoma yield in prospective studies is generally lower, varying between 12 and 22% using colonoscopy13 14 17 and 5.3 and 21% using 60 cm flexible sigmoidoscopy 1819 This disparity results not only from differences in study design, but also the age and strength of the family history of the individuals screened.…”

Impact of a Family History of Colorectal Cancer on the Prevalence of Advanced Adenomas of the Rectosigmoid Colon at Flexible Sigmoidoscopy in 3147 Asymptomatic Patients

“…At first glance our results might appear at odds with clinical and epidemiological studies which show an almost twofold increase in the risk of CRC and adenomas between patients and first-degree relatives (3, 5, 7-10). However, these studies are not uniformly confirmatory and inconsistences are common (3)(4)(5)(6)(7)(8)(9)(10). Further complicating the picture is the lack of a genetic explanation to account for a hereditary risk in late-onset CRC (17,18).…”