Two tests predict inherited cancer risk

Free written screening determines likelihood of developing colon disease

September 29, 2006|By Dennis O'Brien | Dennis O'Brien,Sun reporter

Two research teams have developed written tests - free and available on the Web - to help doctors predict your risk of developing genetically inherited colon cancer.

One group, from the Johns Hopkins Bloomberg School of Public Health, says it has validated its screening technique by testing it on 279 colon cancer patients.

Another team, from Boston's Brigham and Women's Hospital and Dana-Farber Cancer Institute, compiled its screening questionnaire after a five-year study of clinical and genetic data from nearly 2,000 patients with personal or family histories involving the disease.

Reports of both were published this week in the Journal of the American Medical Association.

One problem with cancer screenings based on family history is that they require patients to provide detailed information that they might not have or remember about any cancer running in their families. And the new tests are no exception.

The Hopkins test, for instance, asks patients whether there's any history of endometrial cancer among their aunts. "That's not something most people carry around in their heads," said Dr. Scott Ramsey, a researcher of hereditary colon cancers at the Fred Hutchinson Cancer Research Center in Seattle.

But the Hopkins technique works even if patients can't provide such details, said Sining Chen, lead researcher of the Hopkins report. "The more you know, the more accurate it is. But you don't need to know everything," she said.

Experts say the screenings are an important first step in determining a patient's cancer risk. Researchers also have developed ways to use family histories to assess the risk for certain kinds of breast cancer in women.

"I think it's important work," said Dr. Lisa A. Boardman, a gastroenterologist who diagnoses colon cancer at the Mayo Clinic in Rochester, Minn. "It's important that these screening techniques are looked at and evaluated, and what's more important is that patients and physicians keep a focus on the familial links to cancer."

An estimated 150,000 people are diagnosed with colon cancer each year in the United States and 56,000 people die from it, making it the second-highest cause of cancer deaths, according to the American Cancer Society. The risk of colon cancer increases greatly with age, but chances of survival improve when it's detected early.

Most colon cancers occur in people with no family history of it, experts say. In cases where there's a genetic link, there is often an obvious sign, such as early onset or multiple cases in the same family.

But up to 5 percent of people with colon cancer have Lynch syndrome, a specific type with a less-obvious genetic basis. The new screening techniques are designed for those patients, the researchers say.

The screenings are a first step for patients who suspect they have colon cancer or have been diagnosed with some form of the disease. As a follow-up, patients often have tumors tested or undergo about $2,500 worth of genetic testing to determine whether they have Lynch syndrome.

Lynch syndrome is characterized by defects in three genes - MLH1, MSH2 and MSH6 - that normally help repair problems that occur in the genetic coding process whenever the body produces new cells.

Experts say identifying Lynch syndrome is important for deciding on treatment options and informing patients that their children or siblings are also more likely to have the disease, researchers say.

Women with Lynch syndrome also are at increased risk of uterine and ovarian cancer because of genetic links to those diseases, exerts say.

Doctors recommend that those with Lynch syndrome have a colonoscopy once every one or two years, beginning in their early 20s and annually after age 40, said Dr. Francis Giardiello, a co-author of the Hopkins report and a professor of medicine at the Johns Hopkins School of Medicine. That compares with once every 10 years for those older than 50 in the general population, Giardiello said.

The new screening techniques are designed as improvements to two existing screening techniques, the researchers say.

When doctors use the existing techniques - one is known as the Amsterdam Criteria and the other the Bethesda guidelines - they can either falsely report signs of Lynch syndrome or miss cases, they say.

The techniques were developed by a consensus of experts and have definite cutoff points for inclusion based on a complicated set of family history questions.

Both the Hopkins test and the questionnaire developed by the Boston group give patients a likelihood - based on a percentage figure - that they will develop colon cancer.

"The correct outcome may be more nuanced than a yes or no outcome, and the better option is to have a likelihood as to whether you have Lynch syndrome," said Dr. Sapna Syngal, a co-author of the Boston report who is director of gastroenterology at the Brigham and Women's Hospital and Dana-Farber.

The Hopkins researchers checked their test by predicting the rate of Lynch syndrome among 279 cancer patients whose family histories had been entered into cancer registries at Johns Hopkins, Memorial Sloan-Kettering Cancer Center and an international colon cancer family registry.

The Boston researchers' questionnaire was validated using the personal histories of 1,016 patients who had sought medical help because they suspected they might have colon cancer.

Both methods were about 10 percent more accurate, correctly reclassifying dozens of patients missed by the current systems, the researchers say.

The new questionnaires are available on the Web, but the researchers recommend using them with help from a physician or a genetic or cancer counselor.

The Brigham and Women's Hospital questionnaire is available at dfci.org/premm.

The Hopkins software, known as MMRpro, is available at astor.som.jhmi.edu/Bayes Mendel.

dennis.obrien@baltsun.com

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