Test marks bladder cancer risk

BROWN (US) — A simple blood test can accurately detect markers of bladder cancer that risky exposures leave behind.

The test measures a pattern of “methylation,” a chemical alteration to DNA that affects which genes are expressed in cells associated with bladder cancer.

Methylation is affected by exposures in the environment, such as cigarette smoke and industrial pollutants, so abnormal patterns of it in the body could be indicators of an increased likelihood of disease.

“What we might be measuring is an accumulated barometer of your life of exposures that then put you at risk,” says Carmen Marsit, assistant professor of medical science at Brown University.

“Will you ever really figure out if eating something when you were 12 gave you cancer? Instead we can use these kinds of markers as an integrated measure of your exposure history throughout your life.”

Details of the research are reported online in the Journal of Clinical Oncology.

Prediction or early detection?

To create the test, scientists at Brown and Dartmouth University studied the blood of 112 people who had bladder cancer and 118 who didn’t. That gave them the tell-tale pattern of methylation to look for in immune system cells in the blood. Then, under blind conditions, the test was applied to the blood of a similar number of people who either had the cancer or didn’t, and made their predictions.

It was possible to determine who had cancer and who didn’t, based solely on the methylation pattern they observed.

Controlling for the exposure to known risk factors like smoking that the patients reported, people with the methylation pattern were 5.2 times more likely to have bladder cancer than people who did not have the pattern.

Because the samples used in the study came from people who already had the cancer, Marsit acknowledges it can’t be certain without further research whether the methylation markers in their immune system cells were predictors of cancer (i.e., they were present before the cancer began growing, as the team’s hypothesis suggests) or simply indicated that the cancer was already there (i.e., they are a consequence of the cancer).

But at a minimum, the study proves that the cancer is associated with a methylation pattern that can readily be detected in the blood, Marsit says.

For cancers that are buried deep in the body and are therefore hard to detect, such as bladder cancer, a minimally invasive test that provides either prediction or early detection of cancer could make a big difference in improving a patient’s prognosis, Marsit says.

Testing for methylation in blood cells could also be similarly applicable to other cancers.

The study was funded by the National Institutes of Health and the Flight Attendants Medical Research Institute.

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