Early detection of colorectal cancer can save some lives. The perfect screen for the disease would be noninvasive, inexpensive, convenient, and highly accurate. Such a test has proven elusive, and researchers continue to look for better ones. This news story reports on a new colorectal screening test that uses a genetic marker to detect changes in DNA that signal colon cancer. Although the story explains how the test works and why the American Cancer Society recommends it, it fails to provide most of the key information readers would need to weigh the potential benefits and harms for themselves.
The story does not explain the quality of the science to support the screen. It also fails to quantify the screen’s benefits: What is a 50-year-old person’s chance of dying of colon cancer over the next 30 years if he or she does not screen for colon cancer (answer: about 2%)—and how does that compare with that person’s chance of dying of colon cancer if he or she undergoes noninvasive stool DNA screening? (The article doesn’t say, but the answer is probably a little less than 1%.)
The story does not mention potential harms. How many cancers does the new test miss (false negatives)? What is the rate of cancers it detects which turn out to be false positive? How many people with a healthy bowel are hospitalized with a serious complication incurred during the follow-up confirmatory colonoscopy?
The article also fails to cite an independent expert. The only person interviewed is the scientist who led a research team that developed the screen.
Finally, the story’s opening paragraphs are designed to alarm readers (some 150,000 people will be newly diagnosed with colon or rectal cancer this year) and prod them to action (if you are over age 50, get screening to detect and, presumably, cure early cancer). Readers could easily come away with the impression that colorectal cancer causes death in a significant proportion of people over the age of 50. Although any life lost prematurely to colorectal cancer is a terrible misfortune, the chances that it will happen to the average reader are quite small. To our eye, the story is teaching fear when it should reassure.
The story notes that one test that was available through June 1 costs about $800. It also mentioned that some insurance and health plans covered the cost partially or in full.
The article says that experts at the American Cancer Society have added the newly recommended stool DNA screen to its screening guidelines because many people are averse to the leading alternative–invasive, inconvenient, and expensive colonoscopies. But when it says the screen is “a huge step forward” that can “significantly increase the rate of detection,” the story’s quantification of benefits is more hype than help. By how much will this screen reduce the likelihood that someone will die of colorectal cancer? How many people over the age of 50 will need to be screened—for how long, and how often—to prevent one death by colon cancer? How does that compare to other screening methods? (For example, with the traditional fecal occult blood test, about 1000 people over the age of 50 must be screened for 10 years to prevent one death from colon cancer.) Is there evidence that "you could reach a lot of people and prevent deaths from happening every day of the year"? Compared to other methods, is there any added benefit for people whose genetic makeup increases their likelihood of colorectal cancer?
The story makes a brief pass at discussing harms when it says: "Compared to more invasive procedures, the test still might miss some polyps and cancers and may need to be repeated more often. If results are abnormal, a colonoscopy would still be required." But readers should be told how many cancers does the test miss (false negatives)? What is the rate of false positives—and how many people will believe they have colon cancer, when in fact they don’t? How many people will find themselves hospitalized with a serious complication caused by a follow-up confirmatory colonoscopy?
The reader is led to believe that there must be high-quality evidence to support the stool DNA screen for colorectal cancer, since the American Cancer Society has added the test to its screening guidelines. Is this an accurate assumption? The story provides no information about the quality of the evidence to support the screen. How accurate is the stool test? What is the sensitivity, specificity, etc.?
The story’s first several paragraphs are designed to alarm readers (some 150,000 people will be newly diagnosed with colon or rectal cancer this year) and prod them to action (if you are over age 50, get screening to detect and, presumably, cure early cancer). Although any life lost prematurely to colorectal cancer is a terrible misfortune, the chances that it will happen to the average reader are quite small. About 2% of those over age 50 will die of colorectal cancer during the next 30 years if they don’t receive screening, and less than 1% if they do. To our eye, the story is teaching fear when it should reassure. It is problematic that the only reasons given for NOT having a colonoscopy are: "fear of doctors, the prospect of being poked and prodded in strange places, lack of insurance to cover the costly test"; another perfectly sane reason is that a person made a well-informed decision against colorectal cancer screening. The story does not even consider that many patients are making a choice here.
The only source cited in the news story is the researcher whose team developed the stool DNA test. There are no independent sources.
The story mentions other screening alternatives, including colonoscopy and CT colonography (or virtual colonoscopy). But it does not mention traditional fecal occult blood testing, the mainstay stool test for decades. And it provides only a cursory comparison of the advantages/disadvantages of the new test compared with existing approaches.
It’s clear from the story that one stool DNA test has been commercially available since 2003. Others will be available later in 2008 and in 2009.
The story explains that stool DNA screening is relatively new, with one product on the market and others on the way.
The story borrows a phrase from a company press release, saying the noninvasive stool test can be used “in the privacy of one’s home,” but it does not appear to be overly reliant on a press release.