Researchers are one step closer to telling prostate cancer patients if their cancer is likely gone for good, that they are cured. Conventional tests used to measure prostate-specific antigen (PSA), which signals the presence of cancer, are not sensitive enough to detect low levels of PSA, and in about 40 percent of cases, cancers return.

A new nanoparticle-based test, developed by Nanosphere, Inc. and used by researchers at University Feinberg School of Medicine and the University International Institute for Nanotechnology, is 300 times more sensitive than conventional tests, offering patients an earlier and more definitive answer to whether they are cured.

"With the conventional tool, you have to wait years to detect a rise of PSA, therefore you have to wait years before you tell a patient they're recurring," explains Chad Mirkin, co-principal investigator. "What this new test does in principle, is it allows you to define disease cure [without waiting the traditional seven years]."

"We think that identifying that no-evidence-of-disease state years earlier with a high-sensitivity test, you'll be able to knock years off that. And that's worth a lot from a patient state of mind perspective. You can tell them, 'Hey, you're not going to die from this disease.' People who have this disease want to know that," he says.

This study, which confirms Mirkin and co-principal investigator C. Shad Thaxton's 2009 findings, was conducted as a retrospective study. The researchers obtained stored blood serum samples from prostate cancer patients who underwent prostatectomies. These samples showed undetectable -- or zero -- levels of PSA, explains Thaxton.

Using a conventional test, "a urologist might say the PSA is undetectable or the PSA is zero," Thaxton says. "Either one, the truth of the matter is, when we looked with a more sensitive assay (blood analysis), it detected PSA at a much lower threshold. It detected PSA, and in fact it's not zero."

But Mirkin points out that level numbers don't necessarily matter. What matters is detecting if there is a steady amount or an increased amount of PSA in the blood over the years.

"All baseline amounts are different among patients," Mirkin says. "[You have to] look at whether the levels are rising significantly or not."

Thaxton adds that the researchers found higher levels of PSA in patients who had unfavorable clinical parameters -- advanced or aggressive cancers -- compared to lower levels of PSA in patients with favorable clinical parameters. This was an indicator of recurrence.

More Industry Headlines