January 01, 2017
Pomper:New approach links radioactive molecules to PMSA, a substance on prostate cells.
Is there any prostate cancer outside the prostate? What if there are just a few cells? No one has ever been able to see the answer to this question before. But now, thanks to Steven Rowe, M.D., Ph.D., and Martin Pomper, M.D., Ph.D., in the Russell H. Morgan Department of Radiology and Radiological Science and a multidisciplinary team that includes chemists, biologists, radiologists, urologists, and oncologists, the answer is visible.
In pioneering work, the team has managed to link radioactive molecules to prostate-specific membrane antigen (PSMA), a substance on the outside of prostate cells. These molecules show up on PET scans, and in studies, the team has been able to “increase dramatically the detection of sites of prostate cancer in men who have newly diagnosed disease and are being treated with surgery, in men who have previously had surgery but whose lab tests now indicate that they have suffered a relapse, and in men with known widespread disease,” says Pomper. This remarkable work already has helped tailor treatments in Hopkins patients with prostate cancer, and will soon be more widely available in larger clinical trials at Hopkins and other hospitals. Because of its promise — not only to see cancer but to target new treatment — the primary imaging agent developed, known as DCFPyL, has been licensed to Progenics Pharmaceuticals for commercial distribution. The radiotherapeutic agents made by the Hopkins team have been licensed to Advanced Accelerator Applications for commercial manufacturing.
Where the Cancer Is
What you’re seeing is something no one has ever been able to see before: all the sites of metastatic prostate cancer. Some of them are too small to show up on conventional imaging, and the only way we can see it now is that Martin Pomper and colleagues figured out how to “tag” individual prostate cancer cells with a radioactive dye that sticks to PMSA — prostate membrane-specific antigen. The red arrows point to new outcrops of cancer in unexpected places well beyond the pelvis, including the lungs and liver.
Now, that’s a lot of cancer, but it doesn’t mean that this cancer can’t be treated. Some of these areas may respond to hormonal therapy, some may be big enough to target with radiation, and some may respond to chemotherapy — including specialized, experimental treatment that uses this same PSMA-targeting approach. Knowing where the targets are is a huge step toward determining how to reach them.