Long sought in breast imaging, a new biomarker for positron emission tomography (PET) scans could provide a "fingerprint" for cancer, possibly lessening doctors' reliance on costly and invasive needle biopsies.

According to recent studies conducted by researchers at Thomas Jefferson University in Philadelphia and published in The Journal of Nuclear Medicine, unlike earlier PET agents, a marker called NVB-64 appears to reliably illuminate potentially deadly growths in the breast.

NVB-64, also known as 64Cu-TP3805, works by recognizing specific genetic changes expressed by tumor cell receptors, VPAC1 receptors, which respond to the vasoactive intestinal peptide, a hormone that serves several different functions throughout the body.

Mathew Thakur, Ph.D., professor of radiology and director of the Laboratories of Radiopharmaceutical Research and Molecular Imaging at Thomas Jefferson University Hospital, was principal researcher for the studies.

"The basic concept is quite novel," says Dr. Thakur. "Hypothetically it can detect all breast cancers. It can eliminate benign tumors [from consideration], and it can detect the cancer at an early stage."

Biopsy alternative?

Needle biopsy is the conventional way to determine tumor malignancy and the "gold standard" for identifying ambiguous masses detected by imaging. But it's expensive, and most women who undergo them do not have cancerous tumors.

"There are about 6 million biopsies performed every year and 80 percent of those find benign pathologies at $5,000 per biopsy," Dr. Thakur says. "That is close to $30 billion."

The new PET biomarker, developed by NuView Life Sciences in Park City, Utah, if proven reliable, would be a faster, cheaper alternative for some women.

NuView says, unlike a needle biopsy, PET imaging would provide same-day results, eliminating the anxiety patients experience waiting for tests to come back from the lab.

It would also cut costs significantly for patients and insurers. The price of the NVB64-PET scan is anticipated to be around $2,000. This translates to a 60% cost saving over a typical needle biopsy of the breast.

FDG lacks specificity

Another PET radioisotope called fluorodeoxyglucose (FDG) is already FDA approved and in wide use for imaging breast tumors. It works by looking for metabolic changes in glucose consumption that indicate cancer formation, but NuView argues it leaves many tumors undetected and can't determine malignancy with any degree of certainty.

"FDG misses almost 30 percent of malignancies," says Dr. Thakur. "Although there are a lot of strides that have been made, we cannot distinguish benign tumors from malignant tumors."

But Dr. Thakur posits that the odds are better with NVB-64. In one of his recent studies, Dr. Thakur and his colleagues looked at how the two PET agents detected eight malignant and two benign breast tumors in mice. While NVB-64 PET uncovered all eight malignant growths, FDG picked up just four. And only FDG, not NVB-64, turned up the two benign growths. Human trials using the NVB-64 biomarker are now underway.

Dr. Michael Graham, president of the Society of Nuclear Medicine, believes the research looks promising.

"This seems to be an empiric finding," he says. "[VPAC1] has turned out to be a receptor that is upregulated in a number of malignancies, not just in the breast, but in others including the prostate."

The reason, he argues, is that FDG's glucose use tracking isn't as specific as NVB-64's approach.

"Tumors use glucose rather inefficiently. [FDG] has turned out to be extraordinarily useful in identifying sites of tumors, but it's not specific for tumors," says Dr. Graham. "This [VPAC1] receptor is not 100 percent unique to cancer cells, but it's likely that this is going to be fairly sensitive and specific, but we won't know until more clinical trials determine how useful it's going to be."

Nonetheless, Dr. Graham says this method will likely not replace biopsy. Rather, it will help in difficult cases. He believes more studies should determine its efficacy as an alternative to biopsy and which patient populations would most benefit from these imaging studies.

"The place for an agent like this would be in sorting out the indeterminate mammograms," says Dr. Graham. "If a mammo were clearly positive or clearly negative you would go straight toward getting a biopsy."

Kathy F. Mahdoubi contributed to this report.