Researchers at two Philadelphia universities are working on a joint project they say could lead to an inexpensive, simple device that women could use at home for detecting breast cancer in its earliest stages.

Scientists at Drexel University and the University of Pennsylvania are developing a battery-operated, hand-held device they say uses lights and detectors to "see" metabolic changes.

Cancer specialists and researchers stress that the device has not been subjected to enough tests to reach any conclusions about its effectiveness — and that even if it does work, it would take years to reach market. They also say that such technology would never replace what is now the gold standard for testing: mammograms.

"It's very important that we don't overstate this; it is a first step," said Debbie Saslow, director of breast and gynecologic cancers at the American Cancer Society.

The prototype is a black plastic box about the size of a deck of cards with two tiny light-emitting diodes, or LEDs, on one end. The LEDs use near-infrared light that travels deep into breast tissue, said University of Pennsylvania biophysicist Britton Chance, who invented the device six years ago.

"We want to reach underserved and undercompliant women, who often have difficulty getting medical care or wait until it's too late," Chance said.

A joint research and development team from Penn and neighboring Drexel has been working for four years on testing, funding and marketing for the so-called NIRScanner.

The device makes steady low beeps as a woman moves it along her breast. It uses a type of almost invisible light that travels deep into breast tissue; as the machine nears a tumor the beep tone gets higher, and as it moves away the tone gets lower.

A microchip stores the information on the size and location of the tumor as the patient performs the self-examination. That information can later be analyzed on a computer by the patient's doctor.

In a small clinical trial involving 100 women, the prototype correctly spotted breast cancer in 32 of the 34 women who previously had been diagnosed, with no false positives, the researchers said. The researchers said that result is in line with MRI results and better than mammograms.

But no conclusions can be drawn from a small group that has been "enriched" with a high number of cancer patients, Saslow said.

"In real life if you had 100 subjects, none of them (statistically speaking) would have breast cancer," Saslow said.

"What really matters is having a large clinical trial — probably recruiting women in the thousands — without an enriched set of patients," she said. "Otherwise it doesn't mean a whole lot."

Drexel biomedical engineering professor Banu Onaral, who leads the research effort with Chance, said that the optical scanner would act as a prescreening tool that women would use at home in conjunction with their regular breast self-exams — not in place of other screening methods.

The idea is based on the physical changes that happen when a tumor grows.

Extra blood vessels develop that supply the tumor with nutrients and oxygen. That means the tumor has a blood supply that's much greater than the surrounding breast tissue.

Also, tumors consume more oxygen than healthy tissues. So the levels of hemoglobin, an oxygen-carrying blood protein, are different in normal tissue and tumors.

The researchers said their device's near-infrared light spots tumors by "seeing" those variations in blood volume and oxygen. Unlike mammography, ultrasound and MRI, which detect anatomical changes, their device looks at physiological changes that occur at the earliest stages of breast cancer, they said.

The researchers said they would need about $9 million in public and private funding to put the device through large-scale clinical trials, and an additional $7 million to get the scanner produced if it won regulatory approval. The trials and production would take more than five years, they said.

Other noninvasive devices using optics technology are being tested as potential breast cancer detectors at several other research centers around the country. At University of California, Irvine, biomedical engineer Bruce Tromberg has been working on an optical breast cancer screening tool for a decade and agreed that it's premature to conclude that such scanners will become commonly used.

"There's a lot of hype around these kinds of things, and it's something patients get excited about and want," Tromberg said. "We don't want to quash enthusiasm of the concept but we also don't want to prematurely raise people's raises hopes and expectations."

"It's a wonderful concept but I can't sit here and tell you it can be done. There's a lot of heavy lifting that needs to be done first."