A unique new bone-targeting radiopharmaceutical agent is earning good reviews by doctors who are seeking more ways to ease the symptoms of patients in the later stages of advanced prostate cancer and symptomatic bone metastases.

Some doctors are now recommending the new-generation radiopharmaceutical to help slow the progress of bone metastases that have spread as the result of castration-resistant advanced prostate cancer, adding some life time and quality to patients. With its low toxicity, the new agent also offers some relief from side effects resulting from other treatments.

“These palliative benefits improve the quality of life for the patient,” said Dr. Laurence Klotz of Sunnybrook Health Sciences Centre in Toronto. Tests have shown that patients might also realize an average life extension of about four months through the use of the radiopharmaceutical agent, he said.  It is administered intravenously.

“We have had a very positive experience with it; patient symptoms were stabilized, and we were getting the expected survival benefits,” said Dr. Klotz. He was a participant in the key clinical trials of the agent in Canada.

Low toxicity benefits for radiopharmaceutical

“It was shown to have low toxicity with significant benefits to patients through randomized testing, with very few side effects,” said Dr. Klotz. It works well for patients who do not want or cannot have chemotherapy, or for those who have stopped realizing any benefits from chemotherapy.

"The relative uniqueness of the radiopharmaceutical in the arsenal of cancer treatments may prove to be an advantage in itself. That is, ways may be established to combine the use of it with the other hormonal agents to render better collective results"

In agreement was Dr. Bobby Shayegan, Head of Cancer Surgery at St. Joseph’s Healthcare Hamilton, McMaster University, who said the new bone-targeting radiopharmaceutical will be “another tool at our disposal to use against cancer.” He reflected on the fact that until recently the prognosis for patients with castration-resistant advanced prostate cancer and bone metastases was not optimistic. “But there has been a burst of drug development activity in the last few years, and these agents are offering excellent quality of life benefits,” he said. 

Most of these drugs have been devised to manipulate hormones. Prostate cancer relies on the male hormone testosterone to progress, so these hormone-based agents have been developed as a response, he said.

A bone-seeking antitumour agent

But this new agent is the only one of these that is a radiopharmaceutical. It has been designed to be “calcium-seeking,” enabling it to attack cancer cells that are embedded in bones as a result of the prostate cancer — the condition of metastases. “This bone-targeted agent has good survival benefits,” said Dr. Shayegan.

Unlike traditional radiation therapy or other radio-isotopes, the new radiopharmaceutical has no contact restrictions, says the maker. The infusion is delivered in an outpatient setting, and takes about one minute for infusion. Patients can immediately have contact with their loved ones.

The new agent is earning accolades from other medical professionals. “It is another arrow in our quiver for battling cancer,” said Dr. Neil Fleshner, Chief of Urology at the Princess Margaret Cancer Centre in Toronto. “This is a novel method of action that is having positive effects.”

He pointed to the early results posted by some of the first patients to receive the drug, saying that the bone markers typical of bone metastases “have dropped nicely. It’s not a cure, but it does improve the quality of life and can extend life.”

As well, the relative uniqueness of the radiopharmaceutical in the arsenal of cancer treatments may prove to be an advantage in itself. That is, ways may be established to combine the use of it with the other hormonal agents to render better collective results, says Dr. Fleshner. “We will hopefully get cumulative effects, to increase the survival time,” he said. This new generation bone-targeting radiopharmaceutical agent is currently under funding review by provincial cancer agencies.