MADISON, Wisc. (
) --An experimental stool-based gene test from
was able to detect 85% of colon cancers and 64% of early, pre-cancers, according to data presented Thursday from a preliminary study conducted by the company and the Mayo Clinic.
Exact Science's Cologuard test matched the colon cancer-detection goal and surpassed the 50% detection goal for colorectal pre-cancers that the company set out in advance.
The 64% detection rate for colorectal pre-cancer in the study is "remarkable," says Dr. David Ahlquist of the Mayo Clinic and the lead investigator in the study, because it means Cologuard, if eventually approved, could be the first, non-invasive gene test that allows doctors to diagnose colon cancer at its most treatable stage. Exact Sciences licensed technology for the Cologuard test from Ahlquist and the Mayo Clinic, both of which receive payments and royalties under an ongoing collaboration.
"If you don't detect pre-cancers, you don't prevent cancer," said Ahlquist, adding that current stool- and blood-based colon cancer tests do a poor job of detecting pre cancers.
Colon cancer is highly treatable if detected early but 40% of adults age 50 or older have not been screened as recommended.
Exact Sciences' Cologuard test works by detecting abnormal DNA in cells that are shed into the stool from cancer or pre-cancerous lesions. If Cologuard picks up abnormal DNA in stool, a colonoscopy is then performed to confirm the diagnosis and, if possible, remove the cancer or pre-cancerous polyps.
The Cologuard results were released Thursday at a colon cancer meeting sponsored by the American Association for Cancer Research. The study of 1,100 frozen stool samples is the first blinded, independent assessment of Cologuard's ability to detect cancer and pre-cancer. Much more work needs to be done before the test is approved, including a large, prospectively designed phase III study that Exact Sciences hopes to start next year.
If all goes well, Exact Science could be in position to seek Cologuard's U.S. approval in 2012. If the test is approved, it could launch in 2013, the company has said.
In addition to the 85% and 64% sensitivity to detect cancer and pre-cancers, results from the study Thursday demonstrated Cologuard had a specificity of 88%, or conversely, a false-positive rate of 12%.
That means Cologuard was able to accurately deliver a negative (no cancer) result in 88% of stool samples that didn't contain abnormal cells indicating cancer or pre-cancer.
Ahlquist says Cologuard was modeled to have a specificity of 90% so the actual 88% result fell a bit short of the goal but is still very acceptable, especially when you consider that established cancer diagnostic tests like mammography carry a 70% specificity.
Doctors today do have access to two, inexpensive colon cancer diagnostic tests that work by detecting blood in stool, but the sensitivity of these tests, especially for pre-cancers, is low and the false-positive rate is relatively high.
The German company
has approval in Europe to sell a test that detects the genetic abnormalities associated with colon cancer in a patient's blood. The test, Septin9, is a potential competitor to Exact Science's Cologuard but Septin9, to date, doesn't do as good a job detecting pre-cancers.
Investors have been keyed on Thursday's data release, pushing shares of Exact Sciences higher in anticipation of positive results. The stock has doubled in price over the past two months, closing Wednesday at $8.35. Shares were up 2% to $8.57 in mid-day trading Thursday.
Exact Sciences ended the third quarter with $34.8 millon in cash. The company is widely expected to raise additional cash ahead of starting the Cologuard phase III study.
--Written by Adam Feuerstein in Boston.
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