Jim Kling

October 29, 2012

LAS VEGAS, Nevada — The second- and third-degree relatives of colorectal cancer (CRC) patients are at increased risk for CRC or adenomas, according to a study presented here at the American College of Gastroenterology 2012 Annual Scientific Meeting and Postgraduate Course.

The results also suggest that the current CRC screening guidelines should be extended to the first-degree relatives of patients who were diagnosed with CRC at 60 years or older.

In the United States, CRC is the third most common cancer. Previous research has shown that first-degree relatives of CRC patients are at increased risk for CRC. For the first-degree relatives of patients with CRC or advanced adenomas who were diagnosed before 60 years, current guidelines call for colonoscopy screening after the age of 40 years.

"Millions of Americans get colonoscopy screening based on family history, so it's important for us to make sure we're offering the best possible [guidelines]," Jewel Samadder, MD, assistant professor at the University of Utah and an investigator at the Huntsman Cancer Institute in Salt Lake City, who presented the research, told Medscape Medical News.

Study Design Corrects for Recall Bias

Many previous studies have relied on patient recall of family histories. "If someone was diagnosed with colorectal cancer, they were asked if they had a family member with colorectal cancer," he explained. This can introduce bias, because a patient might misremember and confuse CRC with, for example, stomach cancer. "In this study, we're confirming every case of [familial] colorectal cancer," said Dr. Samadder.

The researchers conducted a retrospective population-based case-control study to look at CRC risks in the first-, second-, and third-degree relatives of CRC patients. The Utah study population involved 126,936 patients 50 to 80 years of age who underwent colonoscopies from February 15, 1995 to January 31, 2009 at Intermountain Healthcare or the University of Utah Health System in Salt Lake City.

The Utah Cancer Registry and the Utah Population Database were used to confirm all cases of CRC in the family history.

Relatives at Consistently Higher Risk

In the study, 3804 patients were diagnosed with CRC. For each CRC patient, the researchers randomly selected 1 age- and sex-matched control from the colonoscopy population who was free of colorectal neoplasia.

The first-degree relatives of CRC patients had consistently higher risks for CRC than the first-degree relatives of the control subjects (odds ratio [OR], 1.79; 95% confidence interval [CI], 1.59 to 2.03). The same was true for second-degree relatives (OR, 1.32; 95% CI, 1.19 to 1.47) and third-degree relatives (OR, 1.15; 95% CI, 1.07 to 1.25).

For first-degree relatives, the increased risk for CRC was similar if the CRC patient was diagnosed before age 60 (OR, 2.17; 95% CI, 1.44 to 3.27) or after age 60 (OR, 1.54; 95% CI, 1.28 to 1.85).

First-degree relatives were also at increased risk for adenomas (OR 1.82, 95% CI 1.66 to 2.00), as were second-degree relatives (OR, 1.19; 95% CI, 1.08 to 1.31) and third-degree relatives (OR, 1.10; 95% CI, 1.04 to 1.17).

As with CRC, the risk for adenomas in first-degree relatives was similar if the patient was diagnosed before age 60 (OR, 2.04; 95% CI, 1.74 to 2.39) or after age 60 (OR, 1.58; 95% CI, 1.37 to 1.83). Spouses of CRC patients were found to have no elevated risks.

Advocate for Earlier Screening?

The fact that risk is similar in the first-degree relatives of CRC patients diagnosed before and after age 60 is a key finding. "We may want to go back to advocating earlier screening for relatives of CRC patients, regardless of the age at which the cancer occurred," said Dr. Samadder.

"It's a very interesting study and a unique database. The findings for second- and third-degree relatives were surprising. We've been so focused on first-degree relatives, trying to figure out recommendations for the best cost-effective screening strategy. This is going to force us to think a little bit more broadly than we have been. If it holds up to scrutiny, I think this has the potential to affect recommendations," Ronald Vender, MD, professor of medicine at the Yale School of Medicine, in New Haven, Connecticut, who was not involved in the study, told Medscape Medical News.

Dr. Samadder and Dr. Vender have disclosed no relevant financial relationships.

American College of Gastroenterology (ACG) 2012 Annual Scientific Meeting and Postgraduate Course: Abstract 9. Presented October 22, 2012