One in 24 people will be diagnosed with colon or colorectal cancer in their lifetime. Diagnosing colon cancer is difficult because there are often few noticeable symptoms until the cancer reaches an advanced stage. That is why screening is the best way to catch this potentially fatal disease early.

The U.S. Preventive Services Task Force recommends all adults between the ages of 45 and 75 be routinely screened.

Up until a decade ago when a stool-based test was made available, the only choice for screening was a colonoscopy, an invasive procedure that uses a flexible tube called a colonoscope to view the inside of the colon and rectum.

“[F]or now, if you're willing and able to do a colonoscopy or stool-based test, don't switch to a blood test.”

A blood test to screen for colon cancer was recently approved by the Food and Drug Administration. It's undeniably easier, quicker and less invasive. But is it as effective in diagnosing colon cancer as the other two options? A University of Stanford study aimed to find out.

Uri Ladabaum, a professor of gastroenterology at Stanford Medicine and his collaborators from the University of Washington, and Oregon Health and Sciences University, did a meta-analysis, collecting previously published data on six commercially available or in-development blood and stool-based screening tests, as well as the gold-standard, colonoscopy. Using this data, they modeled the relative rate of colorectal cancer occurences and deaths among 100,000 average-risk people who used each screening approach.

Their analysis showed the following:

  • Among the 100,000 people who received a colonoscopy every 10 years, it was projected that nearly 1,550 would develop colorectal cancer and over 670 would die from the disease.
  • For those who took stool-based tests every one to three years (depending on the test) the incidence of colorectal cancer ranged from about 2,200 to 2,500 per 100,000 people. The deaths ranged from about 900 to 1,000.
  • For the new blood tests which are recommended to be conducted every three years, the cases ranged from 4,210 to 4,365. Deaths were about 2.5 times the number in the colonoscopy group.
  • Among people who received no screening, it was projected that nearly 7,500 would develop the cancer and over 3,600 would die from it.

The conclusion was clear. “The first generation of blood tests are a really exciting development in the colorectal cancer screening paradigm,” Ladabaum said in a press release. “But for now, if you're willing and able to do a colonoscopy or stool-based test, don't switch to a blood test.”

Ladabaum added, “Ideally, we want as many people as possible to get screened for colorectal cancer, and that's likely going to mean a combination of different tests being used across the population.”

In addition to getting screenings, the Centers for Disease Control (CDC) recommends taking these steps to reduce your risk of developing colon cancer:

  • Increase your physical activity.
  • Maintain a healthy weight.
  • Eat a diet low in animal fats and high in fiber — making sure you are getting plenty of fruits, vegetables and whole grains.
  • Limit alcohol consumption.
  • Avoid tobacco.

The study is published in Annals of Internal Medicine.