Scientists Reject First Genetic Test Kit for Breast Cancer
GAITHERSBURG, Md. (AP) _ Government scientists rejected on Thursday the first genetic test kit designed to predict which breast cancer patients could relapse after surgery and thus need tougher treatment.
The test detects a gene believed to spur cancer cell growth. Several hospitals already check Americans with small, early tumors for the gene in deciding how aggressively to treat them.
But those tests are experimental, performed with little government oversight and accuracy differs from lab to lab, said Dr. Dennis Slamon of the University of California at Los Angeles.
Oncor Inc.’s Inform is trying to become the first Food and Drug Administration-approved test for the gene.
But an FDA advisory committee on Thursday said Oncor’s study of 244 women wasn’t large enough to prove testing for the HER-2/neu gene either worked properly or was useful in deciding how to treat breast cancer. By a 6-1 vote, the panel said Oncor should study many more women; one panelist recommended 2,000.
The FDA is not bound by advisory committee decisions but usually follows them.
``We are very disappointed,″ said Dr. Sandy Wolman, Oncor’s medical director, who predicted the company would get the additional data within a year. Inform already is sold in Europe.
Doctors diagnose 182,000 Americans with breast cancer every year. Some 100,000 have small, early tumors that haven’t spread to the lymph nodes. Surgery can cure 70 percent of such cases, without the debilitating effects of additional chemotherapy.
But doctors don’t know which women have the curable form and which have aggressive cancer that requires strong chemotherapy to fight off a relapse. So most oncologists today advise all women to take the potent drugs.
``If we can predict which ones have that aggressive form, we could target our (additional) therapy more adequately and spare other women,″ said UCLA’s Slamon, who tests some of his patients for the gene before recommending chemotherapy.
Tumors have a unique tendency to make extra copies of certain genes. Several studies show women whose early breast tumors contain extra HER-2/neu are more likely to relapse. That gene is thought to make a protein that signals cancer cells to grow rapidly, so more genes mean the tumor contains more protein and therefore gets more growth signals, Wolman said.
Oncor’s Inform test finds extra HER-2/neu in tumors. Four or more copies of the gene indicates an aggressive tumor, Wolman said.
In 244 cancer patients diagnosed in the 1980s, those with extra HER-2/neu were 3.3 times more likely to relapse within two years as women without the extra genes. They were 4.5 times more likely to die, Oncor found.
But the FDA panel said Oncor’s study was too small to prove Inform worked. Also, none of the 244 patients tried extra chemotherapy until they had a relapse. Because most cancer patients today get some form of chemotherapy, the panelists wondered if the test would benefit them.
``It’s an interesting investigational tool,″ said panel chairman Dr. Jules Harris of St. Luke’s Medical Center in Chicago. ``But I don’t think it’s a tool that should yet be generally available to a community hospital.″
Countered the University of Maryland’s Dr. George Elias: ``Why can’t we let it ... prove or disprove itself on the marketplace?″
Neither the American Cancer Society nor cancer support groups could estimate how many women currently get experimental HER-2/neu testing. The National Alliance of Breast Cancer Organizations tells patients that, while the gene research is ``encouraging,″ it is unproven and should be used cautiously.
Oncor’s stock dropped almost 44 cents a share to $5.87 1/2 in trading Thursday on the New York Stock Exchange.