The U.S. Preventive Services Task Force is about to recommend that healthy men forgo being screened for prostate cancer with the familiar PSA (prostate-specific antigen) blood test. They base the recommendation on several respected human trials indicating that the screening does not save lives. The announcement is sure to roil an already bubbling controversy over the value of that screening. For context, here is a summary of the arguments that doctors on both side of the question often put forward.
Arguments in favor of PSA screening:
--Catching cancer early, when it is still curable, is important.
--Early detection and treatment can prevent deadly metastatic disease. If you don't find the cancer early, you can miss out on the chance of a cure.
--Patients will be able to tolerate the effects of treatment much better if they are treated at a younger age.
--The overall incidence of deaths from prostate cancer has decreased over the past 20 years; this decline must stem from widespread introduction of PSA testing and treatment.
--We are lucky to have a blood test that, in the absence of any overt physical indicators, can help reveal that a cancer may be present.
--The studies that have been performed on the value of PSA screening need additional longer-term follow-pup; negative results could be the result of evaluating the data prematurely.
--To continue to see death from prostate cancer decline further, even more vigorous screening programs need to be put in place.
--A new trend in caring for men with prostate cancer found by the PSA test is "active surveillance," in which men are not treated immediately but are closely monitored with various follow-up tests; treatment begins when signs indicate the cancer is becoming dangerous and needs treatment. But that practice is akin to playing Russian roulette, because test results can underestimate the stage, or extent of progression, of the cancer.
Arguments against PSA Screening:
--Long-term studies that have followed men for more than 20 years shows no difference in death rates between those screened and those not screened.
--If a PSA level is suspicious, men then need to have a biopsy of the gland; if cancer is found, they need to consider treatment. The weight of the evidence argues that men who go that route do not have a lower death rate from prostate cancer than people who were never screened.
--The average age of prostate cancer diagnosis is 71 to 73; men in that age group are more likely to die of other diseases
--The side effects of treatment can include urinary incontinence, erectile dysfunction, and, in those who opt for radiation, inflammation of the lower rectum or bladder. These side effects cause important alterations in patients' quality of life and are hard to justify given that many patients diagnosed with prostate cancer as a result of the PSA test would never suffered any symptoms from their cancer. And those are not the only risks: Many side effects such as fecal incontinence are underreported.
--There is no credible evidence that low-grade prostate cancer uniformly progresses to higher grade cancers, so early treatment is not necessarily needed.
--Active surveillance can help to avoid excessive treatment in response to a PSA test, while ensuring that men who need treatment get it in time to save their lives. When men have been part of active surveillance programs, the likelihood of their dying of non-prostate cancer related reasons was 14 times greater than dying of prostate cancer, so active surveillance seems like a reasonable way of minimizing the negative consequences of PSA testing. Active surveillance is under continuing study.
I should note that men who have a strong family history of prostate cancer and who are African American have a higher likelihood of getting prostate cancer, so those people will probably continue to get tested. I also think it will be important to continue to do PSA testing in men with enlarged prostates who are treated with drugs known as 5-alpha-reductase inhibitors (Proscar/Finasteride or Avodart/dutasteride), since PSA levels should decrease in response to treatment; if the PSA does not decline, these men may be at higher risk of developing the disease.
In the end, we urgently need a screening test that can distinguish well between prostate cancers that will become life-threatening and those that will not, and we need treatments that come with fewer risks of severe side effects.
Editor's note (10/8/11): The first two sentences of the penultimate paragraph were changed for clarification.