Screening tumors from all colon cancer patients could be a cost-effective way of spotting families at high genetic risk of the disease, a study published Monday suggests.
Of the roughly 160,000 Americans diagnosed with colon cancer each year, about 3 percent have an inherited condition called Lynch syndrome, which involves abnormalities in particular genes that help repair damage to body cells' DNA.
Over time, that unchecked damage is likely to result in cancer: A person with Lynch syndrome has an 80 percent chance of developing colon cancer at some point — often before the age of 50.
Lynch syndrome also carries higher-than-normal risks of developing tumors in the uterus (endometrial cancer) and several other organs, including the ovaries, stomach, liver, and kidney.
Right now, families affected by Lynch syndrome are most often identified based on "clinical suspicion," said Dr. Uri Ladabaum, the lead researcher on the new study.
If a patient has, for example, multiple relatives who've had colon cancer, or a family member who developed the cancer at a young age, a doctor might suspect Lynch syndrome.
The problem with that approach is that it may miss many affected families, said Ladabaum, who directs the gastrointestinal cancer prevention program at Stanford University in California.
Another, more systematic option is to screen all colon cancer patients' tumors for signs of abnormalities linked to Lynch syndrome. If a tumor tests positive, patients can have the far pricier blood tests for detecting Lynch gene mutations, which confirm a diagnosis.
From there, close family members can be offered blood testing. If they, too, have Lynch syndrome, they can take steps to catch cancer early, or possibly prevent it.
Frequent colonoscopies can detect colon tumors early, for instance, or even prevent the disease by spotting pre-cancerous growths (called polyps) that are then removed.
Women may also opt to have their uterus and ovaries surgically removed to eliminate the risk of endometrial and ovarian cancers.
According to the new study, published in the Annals of Internal Medicine, such steps could prolong the lives of women carrying the mutation by up to four years on average.
Some U.S. medical centers are already screening tumors from all colon cancer patients, Ladabaum noted in an interview.
"And there is a growing consensus that this is a good idea," he said.
But whether the tactic is cost effective is unknown.
So for their study, Ladabaum's team used a computer model to estimate the cost effectiveness of different approaches to spotting families with Lynch syndrome.
One was to screen tumors from all colon cancer patients, then go from there. Another was to go directly to genetic blood tests for all patients. A third was to ask patients about their family history, and if suspicions were raised, either test their tumors or go straight to genetic blood tests.
It turned out that tumor testing first, followed by genetic tests if needed, was the most cost effective. (A medical intervention is generally considered cost effective if it rings in at $50,000 or less for every year of life gained.)
The most economical tumor testing involved two different tests, together costing about $400, that zero in on those patients likely to have Lynch syndrome. They would then need genetic testing.
There are several blood tests that look for individual gene mutations linked to Lynch, with each costing around $1,000. Doing the tumor tests first helps doctors know which particular gene mutation to test for, helping to keep the ultimate cost down.
"There's reasonably strong evidence that it would be worthwhile to institute some systematic way of trying to identify these families," Ladabaum said.
But ultimately, he added, the effectiveness of any tactic for catching Lynch rests on cancer-free family members' willingness to have the genetic testing.
"The key really is spreading out the benefit in the family," Ladabaum said.
When a parent has Lynch syndrome, his or her child has a 50 percent chance of having it too. So if a colon cancer patient is found to have it, that patient's children and siblings should ideally be tested.
From there, testing goes in a "cascade," Ladabaum said. If a patient's son, for example, tests positive for Lynch, then that son's children should also be tested; but if that same patient's daughter does not have Lynch, her children would not need testing.
Ladabaum's team estimated that for any of the approaches they studied to be cost effective, at least three to four relatives of each patient with Lynch would have to agree to testing.
"This study suggests it's both medically effective and cost effective to screen all colon cancer tissue," said Dr. Randall W. Burt, who wrote an editorial published with the study.
That's what's already being done where Burt works, at the University of Utah in Salt Lake City.
Still, Burt cautioned that this study was based on a mathematical model, and not patients and families. "We still need further, real-world medical testing," he said.
For now, both Ladabaum and Burt suggested that if people are concerned that they have a strong family history of colon cancer, they should talk with their doctors about it.
A strong family history would generally mean having several relatives with the cancer, with at least two generations in a row affected and at least one person diagnosed before the age of 50.
If you yourself do not have colon cancer, but have a strong family history, it might be possible to have a relative's colon cancer tissue tested, if it is still stored at the pathology lab.
Otherwise, there are the expensive genetic tests. In a recent study, Burt and his colleagues found that when family history suggests a high likelihood of Lynch syndrome, genetic testing may be cost effective.
But that study, Burt said, was also based on a mathematical model.
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