'Mismatch repair-deficient' genetic flaws studied

Tumor cell testing might show if new immunotherapy could target your particular cancer

The more gene mutations hidden inside your cancerous tumor, "the better chance your immune system has to fight back."

That's what Lauren Neergaard, an Associated Press medical writer, wrote recently after a newly approved landmark drug became "the first cancer therapy ever cleared [by the Food and Drug Administration] based on a tumor's genetics instead of the body part it struck first."

Keytruda, an immunotherapy, apparently might help those whose disease is among those with a common genetic flaw — called a mismatch repair defect — carried by seemingly unrelated cancers.

Genetic testing can show if a patient is a candidate for the precision immunotherapy.

Neergaard's story indicates that Johns Hopkins researchers estimate "about 4 percent of cancers are mismatch repair-deficient, potentially adding up to 60,000 patients a year."

Widely available tests to tell who's eligible for the immunotherapy cost between $300 and $600.

The flaw, Neergaard's article says, "is more common in colon, endometrial and gastrointestinal cancers but occasionally in a list of others." 

Dr. Bert Vogelstein

According to Dr. Bert Vogelstein, a cancer geneticist at Johns Hopkins, where the new use for the immunotherapy was discovered, the more mutations in a tumor, the greater the chance that at least one of them produces a foreign-looking protein that is a beacon for immune cells." 

More information on cancer research is contained in "Rollercoaster: How a man can survive his partner's breast cancer," a VitalityPress book I, Woody Weingarten, aimed at male caregivers.