Study: Noninvasive test for colon cancer effective
- Article by: ANDREW POLLACK
- New York Times
- April 18, 2013 - 8:50 PM
A new, noninvasive screening test can detect most cases of colorectal cancer and also many precancerous polyps, potentially helping to sharply reduce the death toll from the disease, according to results of a study released on Thursday.
Still, the results fell short of investor expectations and even those of the company that developed the test, the Exact Sciences Corp., sending its shares down more than 20 percent in afternoon trading on Thursday.
In its news release about the study Thursday morning, Exact Sciences said its test detected 92 percent of the cancers picked up by colonoscopy, and 42 percent of potentially precancerous polyps. It had a false positive rate of 13 percent.
“Precancerous sensitivity, which was the key metric investors were looking at, was well below expectations,” Wedbush Securities analyst Zarak Khurshid told Reuters news service, adding that “lower pre-cancer sensitivity may limit the eventual addressable opportunity for the test.” Khurshid was expecting a 55% detection rate for precancerous polyps.
“The overall results are a huge win over the battle against colon cancer,” said Kevin T. Conroy, the Madison, Wis., company’s president and chief executive officer. We achieved basically the same level of cancer detection as the colonoscopy, and the same level of precancer detection as the Pap smear.”
The study is one of the most extensive for colon cancer screening ever conducted in the United States, Exact Sciences said. It is also a key component in the company’s plans to submit its application to the Food and Drug Administration for permission to begin marketing the test.
The test looks for alterations in human DNA found in a stool sample. The company contends that people will not find it off-putting to deposit a sample of their stool in the company’s collection apparatus and mail it to a laboratory.
The new test, called Cologuard, would not replace colonoscopy. Colonoscopy remains the gold standard for colorectal screening, in part because any polyps detected can also be removed during a colonoscopy, possibly preventing cancer.
But about half of people older than 50, the recommended age to start screening for colorectal cancer, are either not adequately screened or not screened at all, in part because colonoscopy is invasive, uncomfortable, expensive and time-consuming.
Exact Sciences says the noninvasive test could allow more people to be screened, and those with a positive result could then get a colonoscopy.
“For the first time noninvasively, we can detect reliably precancerous polyps,” Kevin T. Conroy, the company’s chief executive, told analysts on Thursday.
There were about 143,000 new cases of colorectal cancer and 52,000 deaths in the United States last year, making it the second-leading cause of cancer death behind lung cancer, according to the American Cancer Society.
Not a ‘holy grail’
Dr. Deborah A. Fisher, an associate professor of medicine at Duke University, who was not involved in the study, said the Cologuard test appeared to be a viable option, but only one of several.
“I don’t think this is the holy grail,” said Fisher, a gastroenterologist who is a consultant to Epigenomics, a company developing a test that could compete with Cologuard. She said it was too soon to tell whether the Cologuard test would actually increase the number of people being screened and said there was no data showing that its use actually prevented cancer deaths.
Fisher said existing noninvasive tests that look for blood in the stool can detect around 80 percent of cancers and 20 to 40 percent of polyps. These tests cost about $25, she said, while the Cologuard test is expected to cost a few hundred dollars.
Exact Sciences said participants in its study also received a stool blood test, known as a fecal immunochemical test. The Cologuard test, the company said, proved to be better than that test in detecting polyps and roughly equivalent in detecting cancer.
The company did not release the data, however, saying it would eventually be published in a peer-reviewed medical journal. The study involved about 10,000 people with an average risk of colorectal cancer. They were screened at 90 sites in the United States and Canada.
Conroy of Exact Sciences said the 42 percent success rate in detecting polyps, while below the company’s goal of 50 percent, was still a powerful result. He said the test caught 66 percent of polyps larger than 2 centimeters, which were more likely to become cancerous than smaller ones.
He also said that since colon cancer developed over many years, if people took the Cologuard test every three years, most polyps would be detected before they could cause problems. Such repeated testing is the reason the Pap test has greatly reduced deaths from cervical cancer, even though Pap tests miss precancerous lesions as much as half of the time.
But Fisher of Duke said yearly use of the less expensive fecal immunochemical test would also eventually detect many polyps.
© 2013 Star Tribune