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Medical Forum / Diseases and Disorders / Prostate Cancer / September 2004not my viewpoint - PSA test 'all but useless' for predicting prostate
leonard - what do you think of how they used their stats? =============== Science Blog is testing a blogging system for readers. It's free, fun and a great way to mouth off. Visit Science Blog Central for an account. Feedback is welcome. PSA test 'all but useless' for predicting prostate cancer Posted on Friday, September 10, 2004 @ 9:15 AM PDT by bjs The PSA test, commonly used as a screening tool for detecting prostate cancer, is now all but useless for predicting prostate cancer risk, according to Stanford University School of Medicine researchers. A study of prostate tissues collected over 20 years - from the time it first became standard to remove prostates in response to high PSA levels to the present - reveals that as a screen, the test now indicates nothing more than the size of the prostate gland. ''The PSA era is over in the United States,'' said Thomas Stamey, MD, professor of urology and lead author of the study published in the October issue of the Journal of Urology. ''Our study raises a very serious question of whether a man should even use the PSA test for prostate cancer screening any more.'' From Stanford University: Stanford researcher declares 'PSA era is over' in predicting prostate cancer risk The PSA test, commonly used as a screening tool for detecting prostate cancer, is now all but useless for predicting prostate cancer risk, according to Stanford University School of Medicine researchers. A study of prostate tissues collected over 20 years - from the time it first became standard to remove prostates in response to high PSA levels to the present - reveals that as a screen, the test now indicates nothing more than the size of the prostate gland. ''The PSA era is over in the United States,'' said Thomas Stamey, MD, professor of urology and lead author of the study published in the October issue of the Journal of Urology. ''Our study raises a very serious question of whether a man should even use the PSA test for prostate cancer screening any more.'' The PSA test measures prostate specific antigen, a protein normally produced by the prostate gland. Stamey published the original findings in 1987 in the New England Journal of Medicine showing that increased blood PSA levels could be used to indicate prostate cancer. However, through the years, Stamey has come to believe that the PSA test is actually not a useful predictor of the amount or severity of prostate cancer. He said elevated levels of that protein actually reflect a condition called benign prostatic hyperplasia, a harmless increase in prostate size. Stamey explained the change in correlation over the years by noting that the tumors encountered 20 years ago were generally so large they generated PSA levels high enough to provide a reasonably good measure of cancer severity. Now that screening is more commonplace in this country, many cancers are being caught earlier and are usually smaller - not generating enough PSA to be a good indicator of severity. Prostate cancer is the most common cancer in men. Stamey cited a 1996 study in which researchers examined the prostates of healthy men who died from trauma, finding that 8 percent of those in their 20s already had prostate cancer. The American Cancer Society estimates that nearly a quarter of a million cases of prostate cancer will be diagnosed in the United States this year alone, and one in six men will be diagnosed with the disease at some point in their lives. Stamey said prostate cancer is a disease ''all men get if we live long enough. All you need is an excuse to biopsy the prostate and you are going to find cancer.'' However, the risk of dying from prostate cancer is very low compared with lung cancer, which is the leading cause of cancer-related death in men, he said. ''Almost every man diagnosed with lung cancer dies of lung cancer, but only 226 out of every 100,000 men over the age of 65 dies of prostate cancer, which is a rate of .003 percent,'' he said, referring to National Cancer Institute statistics. Stamey explained the basic dilemma as such: men whose PSA levels are above 2 ng/ml frequently undergo biopsy, which will almost always find cancer, but this does not necessarily mean that prostate removal or radiation treatment is required. ''What we didn't know in the early years is that benign growth of the prostate is the most common cause of a PSA level between 1 and 10 ng/ml,'' he said. To figure out the PSA test's usefulness in determining which cancers warrant radiation or surgery, Stamey and his team from Stanford's Department of Urology set out to document what was actually found following prostate removal, such as the volume and the grade of the cancer - two indications of the cancer's severity. They then compared those findings to aspects that could be determined prior to surgery, such as how many of the cancers could be felt by rectal examination and the patient's blood PSA level. For the study, they used prostate tissue samples collected by professor John McNeal, MD, who has examined more than 1,300 prostates removed by different urologists at Stanford in the last 20 years. The researchers divided McNeal's data into four five-year periods between 1983 and 2004 and looked at the characteristics of each cancer. They found that over time, there was a substantial decrease in the correlation between PSA levels and the amount of prostate cancer - from 43 percent predictive ability in the first five-year group down to 2 percent in the most recent one. However, the Stanford researchers concluded that the PSA test is quite accurate at indicating the size of the prostate gland, meaning that it is a direct measure of benign prostatic hyperplasia. And Stamey pointed out that it is still very useful for monitoring patients following prostate removal as an indicator of residual prostate cancer that has spread to other parts of the body. ''Our job now is to stop removing every man's prostate who has prostate cancer,'' said Stamey. ''We originally thought we were doing the right thing, but we are now figuring out how we went wrong. Some men need prostate treatment but certainly not all of them.'' If the PSA test is no longer useful, the question remains as to the best course for detecting prostate cancer. Stamey recommends a yearly digital rectal exam for all men over 50. ''If a cancer is felt in the prostate during a rectal examination, it is always a significant cancer and certainly needs treatment,'' he said. Unfortunately, he added, even large cancers often cannot be felt during rectal examination. His group is currently working on finding a blood marker that could indicate more aggressive forms of the cancer that can invade the body. Other researchers who contributed to this work are Mitchell Caldwell, Rosalie Nolley, Marci Hemenez and Joshua Downs. The study was funded by donations to Stamey's Prostate Cancer Research Fund at Stanford. The comments are owned by the poster. We aren't responsible for their content. No Comments Allowed for Anonymous, © Science Blog 2004 knowledge is power - growing old is mandatory - growing wise is optional "Many more men die with prostate cancer than of it. Growing old is invariably fatal. Prostate cancer is only sometimes so." Roy, Here's another vote for you to consider: this Dr. Stamey appears to be telling men in your situation not to have any treatment at all until a tumor can be felt. What a dilemma. jimhoney standard RRP, age 52, cured but was it a waste of time and effort? > Roy, > > Here's another vote for you to consider: this Dr. Stamey appears to be > telling men in your situation not to have any treatment at all until a tumor > can be felt. After my first high PSA reading, my GP did a rectal exam and found nothing. She sent me to a urologist. He did a rectal exam and found nothing. But the PSA was high and he insisted I needed a biopsy. So I got one and it found cancer. When I was next examined, two other doctors did find a tumor on the rectal exam, and it showed up on MRIs. The PSA had gone up over 2 points in 3 months and the Gleason was already at 4+3. If I hadn't had the PSA test, the GP would never have imagined I had cancer. Yet the 4+3 indicated a fairly aggressive case, and the MRI showed a quite large tumor right at the edge of the capsule. I don't know yet if I'm cured, but if I am, it was that PSA test that started the cure going and saved my life. Alan >>Roy, >> [quoted text clipped - 21 lines] > PSA test that started the cure going and saved my > life. My cancer was not quite as bad as yours, but it was a Gleason 7=3+4. From what I've read, I've decided that had it not been detected and treated, the odds of my developing advanced prostate cancer would have been fairly high. I'm not even sure those odds were higher than 50 percent, but even if they were as low as 20 percent, that is not a risk I would want to take if I had a choice. Stamey and those who think like him would argue that if indeed we we benefited from early detection and treatment, then we are just rare cases, but they have absolutely no direct evidence that such is the case. > Alan >> Roy, >> [quoted text clipped - 23 lines] > > Alan My cancer would never have been found if I hadn't seen a new resident at the VA hospital who believed that all men over 50 should have a PSA test. Gary Nichols > Roy, > > Here's another vote for you to consider: this Dr. Stamey appears to be > telling men in your situation not to have any treatment at all until a tumor > can be felt. I did notice that. From everything I've read, if you wait that long, you are significantly more likely to have a recurrence. There is a related issue here. It is well known by now that PSA testing is not a very good way to detect prostate cancer early. Unfortunately, it is one of the few things we have. It is one way to decide if a man should have a biopsy. But if cancer shows up in a biopsy, you pretty definitely do have prostate cancer. So the relevant question is how many men with positive biopsies have cancers which need not be treated. As far as I can tell, Stamey's study doesn't really address that issue. There is the usual argument: PSA tests are leading to the discovery of cancers by biopsy, many men show evidence of cancer on autopsy, so many cancers need not be treated. There are several non sequitors there, but the implication is that very few cancers discovered by PSA testing followed by biopsy ever amount to anything. But there is nothing that I could see in the quoted study which demonstrates that. In point of fact, we just don't know how many of those cancers can be ignored, and more important we don't have any good way to distinguish those that do from those that don't. > What a dilemma. > > jimhoney > standard RRP, age 52, cured > but was it a waste of time and effort? > Roy, > [quoted text clipped - 7 lines] > standard RRP, age 52, cured > but was it a waste of time and effort? Hi Jim..."What a dilemma" says it well. We've known for some time now that the PSA test is not very specific (too many false positives) nor very sensitive (too many false negatives); the efficiency or power of the test is low. Because of the PSA test, we are over treating PCa. PCa is being diagnosed and treated in men who don't really require treatment and they wind up suffering unnecessary morbidities. Moul's study suggests that perhaps as many as 25% of men diagnosed with PCa do not require treatment (his study is now 8-10 years out past diagnosis and the rate of fallout from those practicing WW appears to have plateaued). On the other hand the PSA test does help identify men who have the kind of PCa that requires treatment. Walsh's nomograms show very clearly that if you have PCa that requires treatment, then waiting lessens your chances for a "cure." Few people would choose to act on the basis of a single PSA measurement. However a single PSA measurement within the context of earlier PSA measurements is probably not a bad indicator of the need for further evaluation (antibiotics, DRE by an urologist, free PSA, etc.). If PCa is eventually confirmed through biopsy, and it is low-volume disease, then the true dilemma begins. How do you determine if you have insignificant cancer that doesn't require treatment or aggressive cancer that does require treatment? The PSA test leads to some amount of unnecessary treatment, less, I suspect, among men that have taken the time to learn about their disease and make decisions in partnership with a good urologist / radiologist / oncologist. I believe that when the PSA test is used in an informed manner it is beneficial in ultimately diagnosing PCa and saving lives. IMO, the true dilemma begins after diagnosis of the man with low volume PCa, there aren't any good tests to determine if his disease requires treatment or not...Best wishes and good health, Ron > leonard - what do you think of how they used their stats? > ================ Stamey is a known sceptic about the value of PSA testing, so this is more of the same. I'm not competent to judge the significance of the results in the paper, even if I had it available to read, but I suspect it will get lots of flack from experts such as Walsh and Catalona. But there is an obvious bit of misdirection in one of the quotes below. The likelihood of a man over 65 dying of prostate cancer is given as .003 percent---actually it should be 0.3 percen---and that is compared to the fact that almost all men who are diagnosed with lung cancer die of it. First of all, the relevant statistic would be the death rate from prostate cancer for men who are diagnosed with it, not for the population of all men. In the US, the likelihood of being diagnosed with prostate cancer any time in life is about 16 percent, so the great bulk of men (over 65 or not) are never so diagnosed. In fact about 200,000 men are diagnosed each year with prostate cancer and about 30,000 die of it. So one can get a rough estimate of 30/200 = 15 percent for the likelihood of dying of prostate cancer if you are diaqnosed with it. That isn't quite right because they aren't the same men. It generally takes many years to die of prostate cancer if that is your fate. So one has to set up a fairly involved model to get more accurate figures, but I suspect 15 percent is in the right ball park. I don't know the likelihood of dying of lung cancer if you are diagnosed with it. I suspect it is a bit below 100 percent, but it is certainly high. (My mother had lung cancer and survived it, for example.) But I am certainly willing to believe that lung cancer is 5 or 6 times as deadly as prostate cancer. But it is not 100/.3 ~ 333 times as deadly. (Note by the way that there was an obvious error in the quote. 226/100,000 = .00226 or .226 percent, not .003 percent). > Science Blog is testing a blogging system for readers. It's free, fun > and a great way to mouth off. Visit Science Blog Central for an account. [quoted text clipped - 113 lines] > "Many more men die with prostate cancer than of it. Growing old is > invariably fatal. Prostate cancer is only sometimes so." Aside from the report's implication on the usefulness of PSA testing, I found most remarkable the conclusion that low-grade cancers should not be aggressively treated, presumably even in young men. Now that's going to have all the surgeons and radiologists hopping mad. Bill Denton RP 2/12/02 Memphis > Aside from the report's implication on the usefulness of PSA testing, > I found most remarkable the conclusion that low-grade cancers should > not be aggressively treated, presumably even in young men. Now that's > going to have all the surgeons and radiologists hopping mad. And the young men too. Other researchers have told us that the younger you are when cancer strikes you, the more likely it is to be a virulent and aggressive disease. I have read that about breast cancer and about prostate cancer and it probably applies to others as well. If it's true that 8% of young men have prostate cancer, that may not mean that they don't need treatment. It may in fact mean that they are the ones most likely to die of it and in greatest need of treatment. It's the guys who are in their 70's and 80's who are the best candidates for watchful waiting. Alan >>Aside from the report's implication on the usefulness of PSA testing, >>I found most remarkable the conclusion that low-grade cancers should [quoted text clipped - 17 lines] > > Alan That 8 percent figure is meaningless. It is based on conjectures about how many men that age would show microscopic evidence of prostate cancer on autopsy. Extrapolating from that to assumptions about how many of those men will have a clinically detected prostate cancer any time in life is questionable. |
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