Does PSA Testing for Prostate Cancer Save Lives?
By, Robert A. Wascher, MD, FACS
The information in this column is intended for informational purposes only, and does not constitute medical advice or recommendations by the author. Please consult with your physician before making any lifestyle or medication changes, or if you have any other concerns regarding your health.
DOES PSA TESTING FOR PROSTATE CANCER SAVE LIVES?
Prostate cancer is the most commonly diagnosed non-skin cancer in men. Approximately 190,000 new cases of prostate cancer are diagnosed each year in the United States, and nearly 30,000 American men die of this form of cancer each year, making prostate cancer the second most common cause of cancer death in men (lung cancer, a nearly completely preventable form of cancer, remains the most common cause of cancer death in both men and women). Therefore, according to the American Cancer Society, approximately 1 in every 6 American men will be diagnosed with prostate cancer at some point in their lifetimes, while 1 out of every 35 men will die of this disease.
The death rate due to prostate cancer began to decline in the early 1990s, at about the same time that prostate-specific antigen (PSA) testing became common in the United States. While, few experts dispute that using the PSA test to screen for prostate cancer has dramatically improved our ability to diagnose prostate cancer at a much earlier stage, there continues to be a great deal of debate about whether or not the widespread use of PSA testing has actually played a direct role in reducing the death rate due to prostate cancer. The clinical research data linking routine PSA testing with prostate cancer death rates has, to date, been contradictory, with some studies suggesting that routine PSA testing reduces the risk of dying of prostate cancer, while other studies have found no such relationship between PSA testing and prostate cancer death risk. Even among internationally renowned prostate cancer experts, there continues to be a great deal of disagreement regarding the potential benefits, if any, of routine PSA testing as a screening tool to detect prostate cancer.
Much of the controversy regarding the potential value of PSA testing is, undoubtedly, related to the somewhat unique biology of prostate cancer when compared to other types of cancer. Most types of cancer, if left untreated, will continue to rapidly grow and spread, eventually leading to the death of their hosts. In many cases, however, prostate cancer remains a slow-growing disease that, in many men, causes few if any symptoms, and does not lead to death. Therefore, while many men with potentially aggressive prostate cancers are likely to owe their lives to a PSA test that diagnosed their cancer while still confined to the prostate gland, many other men with slow-growing and non-life-threatening prostate cancers will undergo unnecessary and aggressive prostate cancer treatments because their cancers were, likewise, detected by a PSA test. Since most approved treatments for prostate cancer are associated with a significant risk of complications, many prostate cancer experts worry that too many men are undergoing essentially unnecessary treatment for indolent prostate cancers that might never have been otherwise been detected (and, hence, treated) without a PSA blood test. This concern regarding the potential “overtreatment” of prostate cancer is the primary reason why some experts have advocated against routine PSA testing as a prostate cancer screening tool.
Two new randomized, prospective clinical trials, recently published in the New England Journal of Medicine, are likely to only add fuel to the ongoing debate regarding the routine use of PSA testing to screen for prostate cancer in otherwise healthy men:
The first clinical trial was performed in the United States, between 1993 and 2001. This Prostate, Lung, Colorectal, and Ovarian (PLCO) Screening Trial enrolled nearly 77,000 men, and divided them into two roughly equal groups. The first group was offered annual screening with PSA testing for a period of 6 years and digital rectal exams for 4 years. Among the men in this “screened group,” 85 percent underwent PSA testing and 86 percent underwent digital rectal examinations. The second group was not offered PSA testing or digital rectal examinations, although, as some critics of this study have pointed out, more than half of the men in the second group still actually received PSA testing from their personal physicians by the end of the study, and nearly half of the men in this “unscreened group” also reported receiving digital rectal examinations during the clinical study period, as well. After an average of 7 years of follow-up, 2,820 men in the “screened group” were diagnosed with prostate cancer, while 2,322 new cases of prostate cancer were diagnosed among the “unscreened group” of men. Although there was a 22 percent increase noted in the incidence of prostate cancer among the “screened group” of men when compared with those in the “unscreened group” (at an average of 10 years of follow-up), the death rate among the two groups of men with prostate cancer was essentially the same. Therefore, the authors of this study concluded that, while more cases of prostate cancer were detected among the group of men who underwent routine annual PSA testing and digital rectal examination (when compared to men who were not as rigorously screened), there was essentially no difference in the death rate between men who were rigorously screened and those who were not, after 10 years of observation.
The second prospective clinical study was performed in Europe, and evaluated more than 162,000 men (between the ages of 55 and 69 years) from 7 European countries. As with the previous study, the men participating in this study were randomly divided into two groups. The first group underwent PSA testing approximately every 4 years, while the men in the second group did not undergo PSA testing. This very large cohort of men was followed for an average of 9 years, during which 8.2 percent of the men in the PSA-screened group were diagnosed with prostate cancer and 4.8 percent of the men in the unscreened-group were diagnosed with prostate cancer. Unlike the American study (above), this very large European study found a small but significant improvement in survival among men who were routinely screened with PSA testing, with an observed 20 percent reduction in the risk of death due to prostate cancer among the men who had undergone routine PSA testing when compared to the men who were not tested. At the same time, the absolute difference in the risk of dying of prostate cancer between the two groups of men was quite small (0.71 deaths per 1,000 men), which translates into the need to screen 1,410 men, and to invasively treat 48 men with prostate cancer, before one death from prostate cancer could be prevented. Therefore, the results of this very large prospective, randomized clinical research trial appeared to confirm the concerns of those experts who believe that while routine PSA testing may save some lives, it also subjects many more men to unnecessary treatments that expose these men to all of the risks of such treatment, but without any potential benefit in terms of their prostate cancer.
While these two prospective clinical research trials provide additional ammunition to various camps of experts, the relatively short duration of follow-up included in both studies, in my mind, calls into question the finality of their conclusions. This is because most cases of prostate cancer are relatively slow-growing, and even patients with metastatic prostate cancer can live for many years while receiving hormonal therapy and other treatments. Therefore, it may actually be too early for either of these two studies to draw the respective conclusions that they have published. Indeed, because the death rate from prostate cancer is typically very low during the first 10 years following diagnosis, some experts have already offered a “middle-ground” recommendation for routine PSA testing, suggesting that men who are not likely to live more than 10 years, due to other ailments, should not undergo routine PSA testing. Along the same lines, many experts recommend that men over the age of 75 also not undergo routine PSA testing, as they are unlikely to actually die of prostate cancer if they should develop the disease at this stage of their lives.
So, although the recent publication of these two very important prostate cancer screening trials has generated a great deal of discussion in both the lay and medical communities, they have not, in fact, appreciably altered the debate regarding the routine use of PSA testing as a screening tool for prostate cancer. Fundamentally, this debate will continue to rage on until we are able to accurately identify which cases of prostate cancer actually need to be treated, and which cases can be safely observed. At the present time, we simply cannot reliably determine which patients should undergo invasive treatments for prostate cancer and which patients can safely be offered only “watchful waiting,” and this is really the crux of the dilemma surrounding the issue of routine PSA testing, in my view. That leaves men (and their physicians) to make their decisions regarding routine PSA testing against a backdrop of confusing and contradictory research data, unfortunately. Therefore, at the present time, if you are 50 years old or older (or if you are 40 years old, or older, and you are an African-American man or you have a family history of prostate cancer), you should discuss the issue of PSA testing with your primary physician or your urologist before choosing to have a PSA blood test performed.
Disclaimer: As always, my advice to readers is to seek the advice of your physicianbeforemaking any significant changes in medications, diet, or level of physical activity
Dr. Wascher is an oncologic surgeon, a professor of surgery, a widely published author, and a Surgical Oncologist at the Kaiser Permanente healthcare system in Orange County, California
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