Scientists urged the government Monday to approve a computer system that for the first time would allow doctors to doublecheck women’s Pap smears to ensure no deadly cervical cancer was missed.
An advisory committee to the Food and Drug Administration unanimously agreed that the Papnet system, manufactured by Neuromedical Systems of Suffern, N.Y., will help increase detection of cancer or precancerous changes in cells in some of the 50 million Pap smears performed in the United States annually.
Papnet will not “revolutionize things, it will evolutionize them,” said Dr. Stuart Bentley, a pathologist at the University of North Carolina, Chapel Hill.
“It represents progress” by increasing by as much as 30 percent the proportion of suspicious Pap smears that doctors could detect, agreed Dr. Thomas Sedlacek, a Philadelphia gynecologist.
The Pap smear is the standard test for preventing cervical cancer and catching it in its earliest stages. In the simple test, doctors scrape cells off the cervix and examine them for cancer and precancerous changes in cells that, if removed, can prevent the disease.
Cervical cancer is easily cured if caught early. But laboratories miss abnormal cells in Pap smears about 30 percent of the time.
Until now doctors have had no way to doublecheck the cytologists, who look at hundreds of thousands of cells a day in search of the handful that represent cancer.
The FDA is not obligated to follow advisory committee recommendations but usually does. The FDA panel on Tuesday will consider a Papnet competitor, the Autopath QC, produced by Neopath Inc., of Redmond, Wash.
The panel emphasized that doctors must not use Papnet to diagnose cervical cancer, only as a way to check their existing diagnoses.
Papnet is “a much-needed innovation,” said Kathleen Swiger of the Cancer Research Foundation of America. “Every year women die needlessly of a disease that could be prevented.”
Currently, cytologists put slides containing the cervical cells under a microscope and scan them for signs of abnormalities, basically by looking for differences in the tens of thousands of tiny dots that represent cells’ nuclei. A nucleus that is too large or misshapen can signal cancer, but these abnormalities can be hidden by inflammation from a simple infection, or the cytologist can simply miss one of the tiny cells.
Papnet uses computer technology created to detect missiles in the so-called “Star Wars” defense system. It picks the 128 most abnormal looking cells from every Pap smear and greatly enlarges them.
Laboratories would send every normal Pap smear to a center run by Neuromedical Systems, Papnet’s manufacturer, which would charge about $20 per smear. Neuromedical employees would doublecheck every smear using Papnet.
The system is like proofreading - a person can miss a misspelled word that a computer spellcheck would catch, said Neuromedical chief executive Mark Rutenberg.
In a test of 1,247 Pap smears, Papnet caught 517 of the 534 abnormal samples, for a 97 percent success rate, the FDA said.
Then the company tried to determine how many false-negative Pap smears - the ones the laboratory misdiagnosed - that Papnet could catch. In 228 women with cervical cancer Papnet found 72 whose Pap smears had previously been misdiagnosed. Had the computer been used by those laboratories, it could have diagnosed 92 percent of those women at least a year earlier, said Neuromedical scientist Dr. Laurie Mango.