A new study shows that an alpha-particle emitting radiopeptide—radioactive material bound to a synthetic peptide, a component of protein—is effective for treating prostate cancer in mice, according to researchers at SNM’s 56th Annual Meeting in Toronto. The results could eventually result in a significant breakthrough in prostate cancer treatment, especially for patients whose cancer recurs after the prostate is removed.

“Our study shows that this novel form of treatment has the potential to target and destroy cancer cells with minimal damage to surrounding healthy tissue,” said Damian Wild, University Hospital Basel, Basel, Switzerland, lead author of the study. “Eventually, this therapy could give hope to some of the hardest-to-treat prostate cancer patients and also could be applied to other types of cancer.”

Every year, more than 186,000 men in the United States are newly diagnosed with prostate cancer. The most common types of treatment include surgical removal of some, or all, of the prostate, followed by radiation therapy. More than 30,000 men each year who have had their prostates removed experience recurrence of the cancer. In most of these cases, the disease cannot be localized and treated adequately with conventional treatments; therefore, a systemic treatment that efficiently kills small tumors is needed.

Because tumor cells readily bind with certain peptides, researchers have been able to develop highly specific radiopeptides that bind with tumor cells and treat them using specific therapeutic radioactive substances attached to the radiopeptide. Prostate cancer cells—and many other types of cancer cells—have an overabundance of gastrin-releasing peptide receptors, making the cancer a strong candidate for treatment with radiopeptides.

The study compared two different types of radiopeptides. One group of mice was injected with 213 Bi-DOTA-PESIN, which emits alpha particles that are effective at killing cancer cells. The other group was injected with beta-emitting 177 Lu-DOTA-PESIN, which are also effective in tumor cell-killing, but can also cause damage to nearby healthy cells. Alpha particles are able to kill cancer cells without damaging surrounding healthy tissue. A third group of mice received no treatment.

However, at the maximum tolerated dose, the alpha-emitting 213 Bi-DOTA PESIN was significantly more effective, tripling the survival rate of the mice that received the therapy. The results indicate that the alpha-emitting radiopeptide could provide a new approach for treating prostate cancer and eventually other types of cancer.

Scientific Paper 38: D. Wild, M. Frischknecht, A. Morgenstern, F. Bruchertseifer, J. Boisclair, A. Provencher-Bolliger, H. Maecke, Division of Radiological Chemistry, University Hospital Basel, Basel, Switzerland, Novartis Pharma, SP&A/Investigative and Regulatory Pathology, Basel, Switzerland, and the Institute of Transuranium Elements, Karlsruhe, Germany, “An alpha-particle emitting radiopeptide (213Bi-DOTA-PESIN) for therapy of prostate cancer,” SNM’s 56th Annual Meeting, June 13–17, 2009.

About SNM—Advancing Molecular Imaging and Therapy
SNM is an international scientific and medical organization dedicated to raising public awareness about what molecular imaging is and how it can help provide patients with the best health care possible. SNM members specialize in molecular imaging, a vital element of today’s medical practice that adds an additional dimension to diagnosis, changing the way common and devastating diseases are understood and treated.

SNM’s more than 17,000 members set the standard for molecular imaging and nuclear medicine practice by creating guidelines, sharing information through journals and meetings and leading advocacy on key issues that affect molecular imaging and therapy research and practice.