The Food and Drug Administration’s Oncologic Drugs Advisory Committee is broaching the topic of trials and end points for drugs to treat a segment of the prostate cancer population that is apparently getting rarer as diagnoses become more accurate.
ODAC will meet Sept. 14 to discuss the topic. The FDA’s agenda for the session notes there are no drugs currently approved to treat men with nonmetastatic castration-resistant prostate cancer who have a rising prostate-specific antigen level despite being on androgen-deprivation therapy. ADT is not approved for these patients, and labeling for the class added a warning last October for increased risk of diabetes and certain cardiovascular diseases.
ADT suppresses testosterone, which drives tumor growth, but side effects, in addition to impotence, include osteoporosis and metabolic syndrome, which gave rise to the warnings in labeling for the class. The overall area of prostate cancer is one where, until the last several months, few new treatments were reaching the market.
The committee is questioning whether approval of a new therapy in conjunction with continued ADT would be appropriate for patients with nonmetastatic CRPC.
What makes ODAC’s seemingly simple announcement complicated, said ASCO Cancer Communications Committee Chair Dr. Nicholas Vogelzang, is that "the entity of rising PSA is common, the entity of castrate resistance is common, but nonmetastatic is rare."
In reality, most of the time "nonmetastatic is a mixture of people whose x-rays are missed or not adequately looked at by the radiologist, and it’s a shrinking field" as imaging techniques grow more sophisticated. For example, Dr. Vogelzang said, the new PET F-18 imaging technique (which uses the tracer fluorine-18), "when applied to that population, shows a lot of little spots in the bone that are often missed in the regular bone scan."
However, he said, it could be argued that in men who fit the narrow definition, who’ve had ADT and their PSA is rising, it takes 2-2½ years for new spots to show up under regular imaging. That’s "an end point FDA might find acceptable." Dr. Vogelzang practices at the Comprehensive Cancer Centers of Nevada.
The more urgent unmet need in prostate cancer, in Dr. Vogelzang’s opinion, is in men whose PSAs are rising and who are not castrate resistant. "The elephant in the room" is men who have their prostate removed or radiated and their PSA is rising. "They don’t want to undergo medical or surgical castration. They’re perfectly fine. They have life expectancies we can measure in a decade, maybe more. And they don’t want to lose their testosterone. Who would blame them? Nobody."
This coverage is provided courtesy of "The Pink Sheet." This news organization and "The Pink Sheet" are published by Elsevier.