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Blood test for colon cancer removes the 'ick' factor Add to ...

Despite its cheeky ad campaign, Get Your Butt Seen, the Colorectal Cancer Association of Canada acknowledges that the vast majority of Canadians shy away from being screened for the disease.

But a new blood test, available in Canada as of Dec. 6, may remove the "ick factor" of standard fecal screening tests.

Developed by the German company Epigenomics, the blood test is being marketed as a sanitary and non-invasive alternative to fecal testing and colonoscopy for patients at average risk for the disease.

"The test can easily be integrated at a regular checkup," says Achim Plum, a vice-president for the company.

In a clinical trial conducted by Epigenomics, the blood test detected 67 per cent of colon tumors found in 8,000 patients being screened with colonoscopies. The test's sensitivity rate was 50 per cent for stage 1 colon tumours and 80 per cent for stages 2 and 3.

The test examines blood plasma for changes in a gene called Septin 9, which is present in an "overwhelming percentage" of patients with colorectal cancer, according to Dr. Plum.

Although it is not covered by provincial health-care plans, doctors can order the $445 blood test from Warnex, a private laboratory based in Laval, Que.

Colorectal cancer is highly curable when caught in the early stages, says Barry Stein, president of the Colorectal Cancer Association and a survivor of the disease. But it remains the second-leading cause of cancer death in Canada, after lung cancer.

The mortality rate from colorectal cancer is directly linked to low screening rates for the disease, Mr. Stein says.

Just 4 to 14 per cent of eligible Canadians follow screening recommendations, according to data from Warnex.

Canadian guidelines recommend a fecal occult blood test (FOBT) every two years and a colonoscopy every 10 years for average-risk individuals over age 50. Regular colonoscopies are advised for individuals with risk factors including bowel disease and a family history of colorectal cancer.

Patients with a positive result from a fecal test (or from a Septin 9 blood test) are sent for a colonoscopy, in which the rectum and entire length of the colon are examined using an instrument with a video camera at the end.

Blood and fecal tests are useful screening tools, but they cannot replace this gold-standard procedure, says Terry Phang, a colorectal surgeon at St. Paul's Hospital in Vancouver.

A colonoscopy is the most costly and least appealing test, he adds, "but it's the one that confirms whether you have cancer or not."

During the procedure, a doctor can remove early-stage cancer tumors and mushroom-like growths called polyps, which can become cancerous over time, Dr. Phang explains.

Mr. Stein notes that colorectal cancer is "the only cancer you can prevent before it actually becomes cancer."

But he adds that Canadians are unduly reluctant to deal with fecal samples or get a colonoscopy.

And when they do get symptoms, "they're not talking about it because they're too embarrassed," he says.

Signs of colorectal cancer include constipation, narrow or bloody stools, bloating and abdominal cramps - although the disease may be present without symptoms.

Mr. Stein was 40 when he noticed occasional blood in his stools. "My doctor just said, 'It's probably hemorrhoids, forget about it,' " he recalls. A year later, after a colleague died of colorectal cancer, Mr. Stein made an appointment for a colonoscopy.

The test revealed advanced colorectal cancer that had spread to his liver. Mr. Stein was given a 30-per-cent chance of surviving for five years. After enduring 10 operations and many bouts of chemotherapy, he has been free of the disease for the past eight years.

But Mr. Stein says he regrets he wasn't tested earlier. "I put off doing the fecal occult blood test because of the yuck factor," he says.

Provincial screening programs will likely rely on fecal tests for years to come, since they cost only $15 to $20 per test, Mr. Stein says.

Newer tests such as Septin 9 are not yet cost-effective for broad population screening. But a $445 blood test may be an attractive option for an individual who simply refuses to do a fecal test, he says.

After all, "the best test is the one that people actually do."

Testing alternatives

For Canadians who balk at fecal tests and colonoscopies, there are several other screening tools for colorectal cancer available or in development.

Virtual colonoscopy (CT scan)

Pros: non-invasive view of the rectum and entire colon.

Cons: may not detect all small polyps and cancers; bowel cleansing is necessary; polyps cannot be removed during test; radiation exposure.

Septin 9 blood test

Pros: patient-friendly, detects 67 per cent of cancer tumours.

Cons: expensive ($445); offered by only one Canadian lab (Warnex).

ColonSentry blood test

Pros: patient-friendly; determines current risk of colorectal cancer by looking for changes in DNA.

Cons: not a diagnostic test; does not assess genetic predisposition or future risk; expensive ($392-$449); only available in Ontario and Quebec.

Colo Risk saliva test

Pros: patient-friendly, determines a person's lifetime risk of developing colorectal cancer by looking at genetic markers in saliva combined with environmental risk factors.

Cons: not a diagnostic tool, test still in development.

 

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