There is good reason for guarded optimism among men with advanced prostate cancer. Over the last 2 years we have seen some significant movement with the development of new drugs and treatments for men with advanced prostate cancer. All of these drugs have demonstrated a survival advantage in their clinical trials.
Each of the agents works differently against the disease, suggesting that they may be used either sequentially or in combination to mount the most effective assault on the disease.
One of the newer treatments in the pipeline (not FDA approved) is Alpharadin, or radium-223 chloride. It is a form of injectable radiation that travels in the body targeting cancer cells in the at bone, which is the most common metastatic site for men with advanced prostate cancer.
According to the pharmaceutical company Bayer, Alpharadin was studied in a 922-patient randomized study. At the time of a planned interim safety check it was found that the study was achieving its goal, it wasextending overall survival. The study was halted so that men in the study who were assigned to placebo could be switched over to the treatment.
The interim analysis showed median survival was 14 months for those on Alpharadin, compared with 11.2 months for those on placebo. Both of the groups also were given standard taxotere based chemotherapy. According to Bayer complete data from the study will be presented at an upcoming scientific meeting.
According to Dr. Philip Kantoff, Director of the Genitourinary Oncology Program at Dana-Farber Cancer Institute, Boston, “The results are modest.” Dr. Kantoff wasn’t involved with the study, however, he added, “But from a paradigm standpoint, this is interesting.”
Alpha radiation is potent, Dr. Kantoff added. He also said that the study supports the idea that a survival benefit can be achieved by attacking cancer that has spread to the bone. Bone metastases are one of the main causes of painful symptoms and death among men with advanced prostate cancer whose disease has progressed despite standard hormonal treatments.
The two newly FDA approved drugs, Zytiga (abiraterone) and Jevtana (cabazitaxel) also work, in part, by targeting prostate cancer that has spread to the bone, but they use different mechanisms. Additionally, they are both approved for men after chemotherapy has failed. Provenge, another newly approved drug, boosts the immune system and has been approved for men who are castrate resistant.
Each of the drugs is “pegged at different time points along the cascade” of prostate cancer’s progression, said Michael Yee, biotech analyst at RBC Capital Markets. “The patient wins here because there are so many new options available.”
Other new drug options are in the wings. Medivation Inc. has a triple blockade drug in late-stage clinical trials (MDV-3100) and their interim results are also positive.
Additionally, Exelixis Inc. reported promising results from a Phase II, study of its drug cabozantinib, in advanced prostate cancer. The news, reported at the annual meeting of the American Society of Clinical Oncology (ASCO) in Chicago, was offset by a report of six deaths related to the drug from a separate trial.
Michael Morrissey, president and chief executive officer of Exelixis, said the deaths, involving 1.2% of patients, “were completely in line” with findings of other similar drugs that are already on the market for other cancers. The company plans to launch a late-stage study of cabozantinib in prostate cancer in the second half of this year.
All of these new treatments are exciting and positive, however he real stick in the mud is that in all cases we are seeing only brief (measured in months) life extension. Perhaps, as we learn to sequence these treatments, we will see an exponential magnification of life extension. that is what we really need.
Joel T Nowak, M.A., M.S.W.