By Christine Gorman (Click here for the original article)
The latest findings about the ineffectiveness of PSA testing to screen for prostate cancer has confused many men--and their loved ones. On the one hand is the seeming chance to catch cancer early. On the other hand is the growing realization that many prostate tumors grow so slowly that they will never cause a problem in an individual's lifetime.
After closely examining all the latest data, investigators from the U.S. Preventive Services Task Force concluded in 2011 that the PSA test holds little or no value as a screening test for most healthy men.
Dr. Marc Garnick explored the pros and cons of PSA screening in a feature article in the February 2012 issue of Scientific American entitled "The Great Prostate Debate: Does Screening Save Lives?" [preview]. After writing the article, Garnick, who is a prostate cancer expert and medical oncologist at of Harvard Medical school and Beth Israel Medical Center in Boston, agreed to speak at greater length with senior editor Christine Gorman about the following questions in the prostate cancer field.
Q: Why are medical experts questioning the value of the PSA test to screen for prostate cancer?
In 2009, two very important studies—one from Europe and one from the United States—were published that looked at whether PSA screening saved lives. "The striking thing of these studies, which included tens of thousands of individuals, was that there was no difference in the overall survival of those men who were tested, biopsied, diagnosed with cancer and then treated compared to the control population who were not offered the testing whatsoever," Garnick says.
Q: So if you could summarize, you're saying that you don't live any longer if you get screened with the PSA test and you're subjecting yourself to really bad side effects from treatments for prostate cancer?
"That's the public health policy perspective," Garnick says. "It's obviously more difficult when you have the individual patient sitting in your office--especially a patient with a strong family history of the disease in whom perhaps their brother had the disease, their father may have had the disease and passed away from it."
Q: What is the difference between a PSA test for screening and one used after a prostate cancer diagnosis?
"The PSA test for screening says, 'Yes, your value may be elevated but we don't know yet, short of doing a biopsy, whether or not you do or do not have prostate cancer.' In a patient who has an established diagnosis of prostate cancer, the PSA is very useful," Garnick explains. "So, for example, if a patient has prostate cancer and they're treated for their cancer and the patient, for example, is treated with a radical prostatectomy in which the cancer is thought to be confined to the prostate gland, surgical removal of the prostate gland should actually result in an undetectable PSA value . . . If it's not undetectable either not all the cancer was removed or there may actually be metastatic cancer that has already spread that is causing the PSA not to come down back to an undetectable level."
Q: What is the latest thinking about what to do with a Gleason score in the middle zones?
Garnick says, "the majority of cancers that we see today are Gleason 3+3s. The other cancers are Gleason 7s (3+4 or 4+3). And then we have a group of very high-risk cancers that we call Gleeson 8 to 10 cancers, which are in general are Gleason 4+4 or 4+5 or 5+4. Those are very aggressive, what we call high-grade cancers.
"The problem is trying to distinguish what the biological behavior of a Gleason 6 cancer and a Gleason 7 cancer is going to be. A Gleeson 3+4 or a 3+3 are the real enigmas because those cancers can bifurcate into being cancers that will never cause problems in the patient's lifetime to cancers, which are going to problems months to years after being diagnosed.
"We don't really have right now a good set of molecular markers or other biomarkers that help us predict which type of behavior an individual patient's cancer is likely to experience."
Q: What are the options if you want to get screened with a PSA test for prostate cancer but are still concerned about the potential side effects of treatment?
"The criticism has been that we're over-diagnosing prostate cancer," Garnick says. "I actually think we're not necessarily over-diagnosing prostate cancer, we're actually over-treating prostate cancer . . .
"The recent National Institutes [of Health] consensus conference took a look at these low-grade or low-risk prostate cancers and actually recommended that we more strongly consider active surveillance in a lot of these men who otherwise would have been treated and suffer the potential consequences of therapy."
Q: What does the future look like for men with advanced cases of prostate cancer?
"This is actually one of the most exciting areas in prostate cancer biology," Garnick says. Over the past 30 years, "We've come from orchietctomy, which is surgical removal of the testicles, to estrogen therapy to the use of LHRH analogues—such as lupron and the anti-androgens—to first- and second-line chemotherapy to second-line hormonal therapy to immune therapy to agents that help bone health."