Tuesday night I fell asleep with my radio on. A few hours later I awoke to hear that a “wonder drug” had been discovered for prostate cancer. Exactly what I had been dreaming about. I was half-asleep at the time, so in the morning I set out to find out more. The BBC reported that an experimental drug, abiraterone acetate, which had been tested on patients in a London hospital, represented the “greatest advance” in PC research in 7 decades. It was said to have dramatically shrunk prostate cancer tumors and extended survival in 70 to 80 percent of men with aggressive prostate cancer.
Naturally I wanted to spread the news, but first I needed to get some perspective. I noticed that abiretarone was grabbing headlines in the UK but not in the US. So I wondered how much of this story was hype and how much was hope. Turns out there’s a lot of both.
One advantage I have in writing about this drug is that I actually understand how abiraterone works. In fact, I wrote a related story here called, “The Puzzle of Treatment Resistant PC Is Solved” on June 3rd. That posting described how scientists had solved a mystery about “castration-resistant” prostate cancer. What that means is that prostate cancers needs androgens (male hormones) in order to grow. That’s why “androgen-deprivation therapy” or castration, either chemically or surgically, is standard treatment for men with advanced PC. But scientists noticed that even when deprived of “systemic” androgens (i.e., ones made in the testes and adrenal glands), some prostate tumors were continuing to grow. So the question was, “What is feeding the cancers?”
As I reported then, scientists at Fred Hutchinson cancer center in Seattle found that when the prostate cancers were deprived of testosterone made by the body *they started to manufacture their own*. They did this by using certain enzymes in the cells to turn cholesterol into DHT — a highly potent form of testosterone. And the “androgen manufacturing” was going on even at distant tumor sites.
My thought on hearing this was, “The audacity of this cancer.” Imagine if we humans were cut off from our food supply and could simply push a button that would set a banquet before us! So it became clear that in order to outsmart the cancer we would have to find a way to interfere with the enzymes that were spurring testosterone production. This would achieve a *complete hormonal blockade* and starve the tumor.
Well, folks, that has now been accomplished in the form of abiretarone acetate, the experimental drug we have been discussing. It appears to suppress ALL sources of testosterone and thereby to cause tumors to shrink.
So is this reason to celebrate? I think so. And Dr. Peter Scardino, head of Urology at Memorial Sloan Kettering hospital, was very optimistic when interviewed about this. But I do have to make clear that we do not know the long-term side effects of abiraterone yet, although early ones were reported to be mild. And results for the drug were based on an initial “Phase I” study which included only 21 people. That’s too small a sample upon which to draw firm conclusions — or to announce to the world that a cure for prostate cancer has been found. But it is also true that a Phase II trial which included 250 patients was concluded, and although the results have not yet been officially reported, they are said to be promising. NOTE: A Phase III study of abiraterone acetate, which will include 1,150 patients, began recruiting in April. It is being conducted by Cougar Biotechnology at sites in the UK and the US. If you qualify I suggest you check it out. Eligible men are those who have failed treatment with hormone therapy and taxotere.
See http://clinicaltrials.gov/ct2/show/NCT00638690 on ClinicalTrials.gov.
If things go well, we could have a potent new tool in our arsenal against PC in as soon as 3 years. But remember, abiretarone is not a cure for PC and we don’t know how long it can hold the cancer at bay. But the new drug offers hope to later-stage PC patients and maybe even works on those with early PC. We will just have to wait to find out the details.