(RxWiki News) For most people, colonoscopy screening for colorectal cancer should begin at age 50. If everything looks good, the next colonoscopy happens 10 years later. For folks with a family history of the disease, earlier and more frequent screenings are recommended. But even that may not be enough.
A large study has shown that current national screening guidelines may miss 10 percent of colorectal cancers in people with a family history of precancerous colon polyps.
First-degree relatives (parents, children and siblings) of people with adenomas (polyps that can lead to colorectal cancer) had a higher risk for colorectal cancer than relatives of people without a history of polyps.
Even more distant relatives of people who’ve had adenomas were shown to have elevated colorectal cancer risks compared to people with no family history of polyps.
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N. Jewel Samadder, MD, an investigator from Huntsman Cancer Institute (HCI) at the University of Utah, led this study to delve into the hereditary risk factors for colorectal cancer.
Using records from the Utah Population Database and Intermountain Healthcare and University of Utah Health Care, the researchers analyzed colonoscopy results from 126,936 patients who underwent colonoscopy between the ages of 50 and 80.
The study combined genealogical and cancer data with patient medical records.
Colonoscopies detected adenomas in 43,189 people and advanced adenomas in 5,563 individuals. These people made up the case population.
The researchers matched each of the case patients with controls — people of the same age and gender who had not had any polyps removed.
The study showed that compared to controls, first-degree relatives of individuals with colon polyps had a 35 percent increased risk of colorectal cancer. If the patients had advanced adenomas, the relatives’ elevated risk jumped to 68 percent.
First-degree relatives of individuals diagnosed with colorectal cancer at age 60 or older had a 23 percent increased risk of developing the disease compared to controls.
Second-degree relatives of individuals with polyps had a 15 percent higher colorectal cancer risk than controls.
Even third-degree relatives (cousins, nieces and nephews, great-grandparents) had a 6 percent higher chance of developing colorectal cancer than controls.
Current screening guidelines recommend that first-degree relatives of people diagnosed with colorectal cancer or advanced adenomas before age 60 begin colonoscopy screenings every five years starting at age 40.
Recommendations for relatives of folks diagnosed with colorectal cancer at age 60 or older are the same as the general public, with recommended colonoscopy screenings beginning at age 50.
Based on these findings, the researchers calculated that current screening guidelines would have missed 10 percent of the colorectal cancers diagnosed in relatives of individuals who had been diagnosed with polyps or colorectal cancer.
"Colorectal tumorigenesis [development of tumors] may have a stronger relationship to our genetic heritage than previously thought,” Timothy J. Yeatman, MD, director of the Gibbs Cancer Center in Spartanburg, SC, told dailyRx News.
“Colorectal screening guidelines currently call for earlier colonoscopy in patients who are first-degree relatives of those diagnosed with colorectal cancer or advanced adenomas. Screening guidelines, however, do not address the much more common scenario of a patient with a first-degree relative harboring a simple adenoma,” Dr. Yeatman explained.
“Here they report a 35 percent elevated risk of cancer in the first-degree relatives of those harboring simple adenomas and a 70 percent elevated risk related to advanced adenomas. This study suggests that 10 percent of cancers that could be detected through early screening might be missed using current guidelines,” said Dr. Yeatman, who is president of the Gibbs Research Institute.
“The bottom line is that our genes, and thus our family history, really do have a significant influence on our future cancer risk. We now need to consider a ‘family history of polyps’ as a potentially significant and notable event that may warrant earlier screening colonoscopy,” Dr. Yeatman concluded.
This study was published October 21 in Cancer, the peer-reviewed journal of the American Cancer Society.
The research was supported by the National Cancer institute, the Utah State Department of Health and the University of Utah.
Two of the authors reported receiving fees for lectures from two companies.