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DNA test no substitute for faecal bowel cancer screening

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The Cancer Council has urged people to continue using faecal occult blood test to screen for bowel cancer, warning that a recently-developed blood test is only a third as effective in detecting the disease.

Cancer Council Australia Chief Executive Officer Professor Ian Olver said the faecal occult blood test (FOBT) remained the “gold standard” for bowel cancer screening despite the development of a DNA test by a team of Flinders University researchers.

The new test involves the detection of two genes that ‘leak’ into the blood when bowel cancer is present.

Using blood samples from more than 2000 hospital patients in Australia and the Netherlands who were scheduled for colonoscopy or for bowel surgery, the researchers found the test could detect bowel cancer in 65 per cent of cases, and the detection rate rose to 73 per cent for cancers that were at stage two or higher.

Presenting the findings at the Digestive Diseases Week conference in Chicago earlier this month, Professor Graeme Young, of the Flinders Centre for Innovation in Cancer at Flinders University, said the test could be used in future as an adjunct to the current FOBT screening program.

“A blood test is likely to overcome some of the barriers to screening with faecal tests,” Professor Young said. “It might prove to be acceptable to those failing to participate in screening using established methods, which at the moment are primarily based around faecal tests.”

But he warned that the test should not be seen as a replacement for the faecal test.

“If this test becomes available in the future I think the message would need to be that the faecal test is the best place to start for people who are due for screening. Then the plasma test would be for those people who can’t or won’t screen with a faecal test,” he said.

Professor Olver said there had been mixed messages about the blood test, which he said was only a third as sensitive for advanced adenomas and stage one cancer as the FOBT test.

“New biomarkers for major disease usually attract media coverage, but it is important to remain focused on the evidence,” he said. “As the developers of the DNA test have noted, it could have a role as an adjunct to FOBT.”

Professor Olver said the “outstanding” results achieved by the FOBT screening program confirmed it as the best population screening test: “We cannot risk having this message confused”.

The Cancer Council has urged GPs to continue to encourage asymptomatic patients 50 years and older to screen for bowel cancer with a FOBT test.

Gastroenterologist Professor James St John said the national FOBT program, when fully implemented, had the potential to prevent 70,000 bowel cancer deaths in the next 40 years, and the main focus needed to remain on rolling out the full biennial FOBT screening program.

“We would welcome the addition of a blood-based test if it assists with surveillance, but the focus has to be on what works best to save the most lives, and that is FOBT,” Professor St John said.

Australian biotechnology company Clinical Genomics co-developed the test with CSIRO, and the new test has been clinically validated in collaboration with the Flinders Centre for Innovation in Cancer at Flinders University.

Clinical Genomics Chief Executive Officer Dr Larry LaPointe said the evaluation results “give reason to be optimistic about the prospect of improving screening rates by providing another option for people who can’t or won’t screen for bowel cancer using home-based tests”.

Dr LaPointe said the test could become available in Australia on a “user pays” basis as soon as early spring.

“These results show the test has the potential to underpin a cost-effective blood test that identifies those with a curable bowel cancer. This has the potential to save many lives by complementing existing screening programs,” added Dr LaPointe.
 

Adrian Rollins

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