An international study described in the Oct. 17 Journal of the American Medical Association (JAMA) found that universal tumor testing in all newly diagnosed colorectal patients produced a “modest increase” in finding people with Lynch syndrome.
One in every 35 people with colorectal cancer has Lynch syndrome – an inherited genetic mutation which greatly increases the person’s chance of developing colorectal cancer more than once, plus other cancers (stomach, pancreas, urinary system, brain or skin cancers). Women with Lynch syndrome also face a 40-60 percent chance of developing endometrial (uterine) cancer in their lifetime and an increased risk for ovarian cancer.
Until genetic tests of tumors became available in recent years, Lynch syndrome could only be diagnosed based on a family history of cancers. But even with genetic testing, Lynch syndrome is still significantly under-diagnosed.
The study by Stanford University researchers analyzed data gathered from 10,200 newly diagnosed CRC patients to see which type of screening most effectively detected Lynch syndrome. Testing tumors for the MMR (mismatch-repair) genetic mutation detected 100% of the Lynch cases.
In the U.S. population as a whole, an estimated 1 in 400 persons has Lynch syndrome. “It’s very under-diagnosed right now,” said Heather Hampel, genetics counselor from Ohio State University and member of a CDC task force which has recommended universal tumor screening for several years.
Lynch syndrome is often suspected when someone is diagnosed with colorectal cancer under age 50. But the international study found that only 45% of those with Lynch syndrome were diagnosed at age 50 or younger.
The other clue to Lynch syndrome is a family history with several members of the same generation (especially if diagnosed young) having colon—or uterine—cancer. But today’s smaller families can confuse the family history, unless it is probed further into grandparents, aunts, uncles, and cousins.
“Only 43% of patients with Lynch syndrome had… a family history [in the first generation], noted the JAMA editorial accompanying the study. “The study results should remind clinicians that simply asking about a family history of CRC in a first-degree relative will miss the majority of patients with Lynch Syndrome,” noted Dr. Uri Ladabaum.
The CDC task force first recommended universal testing of tumors in 2009; by 2011 only 42% of hospitals were routinely testing all tumors, noted Hampel. But she has more institutions calling her every week, to ask about setting up universal tumor screening systems.
Sources: JAMA, Oct. 17 2012, Vol. 308 No. 15, “Identification of Lynch Syndrome Among Patients with Colorectal Cancer,” and editorial “Lynch Syndrome in Patients With Colorectal Cancer: Finding the Needle in the Haystack.”