This article is more than 5 years old. Information may no longer be current.
Risk-based system rather than age alone should guide colorectal cancer screening
Click Here to Manage Email Alerts
Colorectal cancer incidence has been increasing steadily among Americans younger than 50 years, the age at which the U.S. Preventive Services Task Force recommends starting routine screening.
This trend has prompted some clinicians and researchers to suggest that screening start earlier.
However, a researcher who launched a 3-year retrospective study to determine the demographic, physical and clinical factors that increase colorectal cancer risk in the younger population proposed a different strategy.
“We should be moving from an age-based system of screening for colon cancer to one that is risk based, because age is only one factor that contributes to risk,” Thomas F. Imperiale, MD, of the VA and Regenstrief Institute at Indiana University, told HemOnc Today. “There have been calls to lower the age for routine colon cancer screening below age 50, but doing that does not make sense at this point. It would simply be a reactive response that would likely result in net harm because we would be screening so many people unnecessarily. Lowering the screening age would be time consuming, costly and not necessarily good medicine.”
HemOnc Today spoke with Imperiale about his research and its potential implications.
Question: What prompted you to initiate your study?
Answer: We are concerned about the rising incidence in colon cancer risk among those aged younger than 50 years. Incidence is decreasing in every age group except for those aged between 25 to 49 years. There have been calls for lowering the screening age, and this reaction is not necessarily well thought out. Our hope is that we can identify factors that associate with people who have early colon cancer so that we might at least consider screening these high-risk people.
Q: How will you conduct the study ?
A: We are using a retrospective, case–control study design. Although this method may be strong, it is not ideal. The ideal method is a prospective, case–control study in which new or incident cases of young colon cancer are identified, detailed information on these patients is collected, and they are matched with three or four controls for whom the same information is gathered. This ensures a representative sample, for whom equally complete information is collected. We are doing a retrospective case–control study using the National Veteran Affairs databases, which are fairly complete and in-depth. Nonetheless, our study is retrospective. We will be limited by the degree and variation of information collected at the time of diagnosis in the cases, and the extent to which information is collected in controls. The advantages of doing this retrospectively are lower expense and shorter time frame for conducting the study.
Q: What are the potential explanations for the elevated rate of colon cancer in the younger population?
A: Nobody really knows for sure. Candidate factors include rising BMI and sedentary lifestyle.
Q: What do you ultimately hope to find?
A: We hope to find factors that will have higher prevalence in our cases compared with controls. For example, it may be weight of a certain magnitude along with a certain degree of inactivity or other lifestyle factors, such as cigarette smoking or ethanol consumption beyond a certain level. It may be that a combination of these variables multiplies the baseline risk severalfold and allows us to identify a subgroup with risk comparable to persons aged 50 years or older. Even though the incidence of colon cancer among people younger than 50 years is rising, the rate is still very low. We hope to identify which factors, once you apply of them, will elevate the risk comparable to those aged 50 years and older so that we may make the case for early screening.
Q: If the study is successful, what are the possible implications?
A: Possible implications are to start screening high-risk persons before age 50. This may be possible if the combination of inactivity, overweight, cigarette smoking and perhaps other diagnoses — such as hypertension or hyperlipidemia — results in a level of risk observed in people aged 50 years and older. Deciding which method to use to screen such high-risk persons will require some thought.
Q: Why is it necessary for those aged younger than 50 years to be screened with measures other than colonoscopy?
A: It is not a question of ‘necessity’ but rather one of need and choice. Less invasive methods of screening have greater appeal and uptake for most people; it is a matter of whether these lesser invasive options will get the job done.
Q: What might future research entail ?
A: Subsequent research could include patient and provider acceptance of a risk-estimating tool, whether and how well it is taken up in clinical practice, and what findings it yields. – by Jennifer Southall
For more information:
Thomas F. Imperiale, MD, can be reached at Regenstrief Institute Inc., 1101 W. Tenth St., RF 231, Indianapolis, IN 46202-4800; email: timperia@iupui.edu.
Disclosure: Imperiale reports no relevant financial disclosures.