Blood test could show colon cancer risk

With the hope of devising a way to better target colorectal cancer screening, the Doris Duke Charitable Foundation has awarded a $2.25 million, five-year grant to a team of researchers to work to develop an easily accessible blood test to determine colon cancer risk. The goal is to create a test that can be used on a broad scale and will be able to differentiate between those who need aggressive screening and intervention against colon cancer and those who do not.

"Right now, we screen everyone, and we can identify less than 1% of those at higher risk with a blood test. We're trying to be able to stratify who is really at risk and better target the resources," said Marcia Cruz-Correa, MD, PhD, a member of the study team and an associate professor of medicine at the University of Puerto Rico.

The research is getting this push because of the increasing recognition that the impact of current colon cancer screening is somewhat limited.

Several medical societies, including the American Medical Association, and numerous public health agencies long have encouraged colon cancer screening as a means to reduce mortality from the disease. Colon cancer screening rates, however, are far from ideal. According to the Centers for Disease Control and Prevention, more than 40 million people older than 50 have not been screened in accordance with national guidelines.

Researchers suspect that this kind of blood test would address some of the barriers to increasing these rates, especially among those who most need it. For example, current screening modalities are resource-intensive. If everyone recommended to get tested actually was, the burden on the health system would be significant. Researchers hope that a means to focus on those at higher risk will address this issue. Also, most screening tests are not very appealing to patients. Knowledge of increased risk may provide an incentive so more of those who should be screened will go.

"By offering a non-invasive test to determine risk, the number of people willing to be screened should increase dramatically," Dr. Cruz-Correa said.

But the work yet to be done is significant. Researchers already know that insulin-like growth factor 2, or IGF-2 -- the main focus of this research effort -- is implicated in cancer development. What they need to determine is its predictive value and how this value changes over time for the general population. This test also needs to be validated in the primary care setting where researchers believe it will make the most impact.

"To identify risk and intervene and reduce morbidity and mortality, in my mind, it has to be in a primary care setting," said Andrew Feinberg, MD, MPH, project leader and professor of medicine at Johns Hopkins University in Baltimore. "If everything works out -- if IGF-2 status is tied to colon cancer risk in people and the blood test is workable -- then IGF-2 status could be the colon cancer equivalent of cholesterol levels as a risk factor for heart disease."

Primary care physicians said an easier way to determine cancer risk would be welcome.

"It's a good line of research," said Thomas Norris, MD, professor in family medicine at the University of Washington School of Medicine in Seattle. "A readily available, cost-effective test that would allow us to assess colon cancer risk would be worthwhile."

But experts questioned if this undertaking would truly lead to a widely available test. All agreed that this research strategy was valid and would certainly lead to a greater understanding of the mechanisms of the disease. It also fits in with overall objectives of developing better ways to detect cancer earlier in less invasive ways.

"It's interesting research, and a test that would predict risk would be important to develop," said Martin J. Heslin, MD, director of surgical oncology at the University of Alabama at Birmingham. "But right now there are more 'ifs' than 'knows.' "