Understanding the USPSTF Anti-PSA Screening Stance: Is the Glass Half Full or Half Empty?

The U.S. Preventative Services Task Force’s recent recommendation against routine PSA screening for prostate cancer in healthy men represents a fundamental philosophical statement about science, medicine, and human psychology and life that needs to be clearly exposed so that it does not appear cloaked in the certainty of a scientific fact.

While not completely devoid of controversy, the “fact set” underlying the widely different interpretations and recommendations regarding PSA-based prostate cancer screening are largely established. Prostate cancer is a major public health problem in this country. In 2010, there were approximately 217,730 new cases of prostate cancer, and 32,050 men died from prostate cancer, the second leading cause of cancer deaths in this country. Against this bleak backdrop, we know that population based PSA screening saves lives. Period. When studied in large, well performed randomized, clinical trials, PSA-based screening results in anywhere from a 20% to 50% reduction in the risk of dying from prostate cancer. However there are caveats that increase the complexity of the interpretation of this seemingly clear result.

Firstly, early prostate cancer, when not diagnosed nor treated effectively, often will then take many years before it may lead to the eventual demise of the patient. Therefore, it takes more than 10 years of observation in these trials before an observed effect on the reduction in prostate cancer specific mortality is clearly observed. This long interval introduces the risk that a patient, even one destined to die from prostate cancer given enough time, may die from some other cause before then. This long interval also underlies the observation that younger men, with longer life expectancies, are more likely to benefit from the early diagnosis and treatment of prostate cancer, than older men with shorter life expectancies. This long “lead time” leads to an uncertain benefit of screening for any one individual; for those men unlucky enough to die of other causes in the early years after diagnosis and treatment of early stage prostate cancer, hindsight dictates that there was no benefit, and there may have even have been harm if treatment was associated with negative side effects. However, for those blessed to live a longer life, and especially those found to have aggressive tumors, the diagnosis and successful treatment of early stage prostate cancer could be deemed a lifesaver. Human psychology dictates that we want to hope for the best for ourselves with respect to the length and quality of our lives, not resign ourselves or plan for the possibility of a far less rosy future. Who among us would like to hope for an earlier death simply to validate a choice to avoid screening for prostate cancer?

Secondly, as effective as PSA is in screening for prostate cancer and reducing prostate cancer specific mortality, PSA is far from a perfect test, and many men without prostate cancer may undergo an ultimately negative biopsy because of a “falsely” elevated PSA test. This factor, which waters down the otherwise successful reduction in prostate cancer deaths, is captured by the terms “number needed to screen” and “number needed to treat”, defined as the number of men who would have to be screened, and the number of men who would have to be treated for prostate cancer, in order to prevent one death. Death from prostate cancer is the preferred measure of success for a screening program for any cancer, however it fails to capture the myriad of negative consequences facing patients who develop advanced prostate cancer that might have been otherwise curable if diagnosed earlier, for example the need for “castration” therapy to control advanced cancer and stave off death. In one carefully performed screening study, it required 234 men to be screened, and 15 men to be diagnosed with prostate cancer to prevent one prostate cancer death. These numbers compare favorably to those for screening programs targeting breast or colon cancer. If one follows the reasoning of the USPSTF, then one should stop screening for all of these important cancers, and simply let the chips fall where they may, diagnosing and treating cancers when they turn up through symptoms, which in the case of prostate cancer, is almost always the sign of advanced, incurable disease. In fact, in 2009 the USPSTF did issue a recommendation against screening mammography for breast cancer in younger women under the age of 50, generating an overwhelmingly hostile reaction from the media, public advocacy groups, and specialist medical groups. However, for those men treated for prostate cancer, especially when complicated by side effects from the treatment, who were not destined to develop metastatic disease or death prior to succumbing to some other ailment, it is hard to argue that they derived any benefit from their diagnosis and treatment.

So what is the correct interpretation of these complex set of facts? For the USPSTF, their response appears to be one of nihilism and futility. “Let’s stop screening for prostate cancer until we can do a more perfect job at finding it and treating it” they appear to be saying. My reaction is a different one and centers on some key recommendations that try and build on the positive aspects of the PSA test, tilting the “risk to benefit” equation more firmly towards prostate cancer screening:

1. Use PSA screening intelligently, and augment it with newer markers like the percent free PSA, the P2PSA test, on the cusp of FDA approval, and the urine PCA-3 that can improve on the specificity of PSA and decrease the number of unnecessary biopsies. We use a range of available data to determine which men may need further testing, rather than apply a simple cutoff PSA value across the board.
2. When performing prostate biopsies, take care to do them as carefully and safely as possible to reduce the risk of infection after biopsy. Since reviewing and improving on our process several years ago, we have reduced the risk of this complication to near zero.
3. Not all men diagnosed with prostate cancer need aggressive therapy. Many, especially older men with other medical problems and small, lower grade tumors, can enter a program of “active surveillance”. However, if we don’t screen and diagnose prostate cancer, we won’t have the opportunity to find and treat the more aggressive tumors amongst them while they still remain curable.
4. Do one’s best to minimize the side effects of prostate cancer treatment, whether it is robotic prostatectomy or image-guided external beam radiation therapy. Improvements in these technologies have progressively reduced the burden of side effects in men treated with them. Experience matters in this regard and we have treated thousands of patients for early stage prostate cancer over the past 18 years, a track record during which I have also striven to improve our technique and outcomes to give men the best chance at living a good quality, cancer-free life.
5. In addition to the standard options for therapy, surgery and radiation, or active surveillance, there is a growing group of researchers exploring a middle ground of “focal therapy” in which only the portion of the prostate affected by cancer is treated, in an attempt to maintain a high cure rate while reducing side effects of treatment. We have been an active participant in these studies from the very inception of the field, which remains promising but still unproven.
6. Support advancement in the overall health of our patients so that they are more likely to live longer and healthier lives, and hope that improvement in the diagnosis and treatment of the other major causes of mortality e.g. heart disease, diabetes, and other cancers continues to improve as well.

Ultimately, each man must decide which is the best approach is for him. We are ready to support and provide the highest quality of care for our patients regardless of which choice they make.

To your health!

Kevin M. Slawin, M.D.

To read what other leading physicians have to say, check out this article from the New England Journal of Medicine and this article also from the New England Journal of Medicine.

 This just in - "President Obama Receives PSA Test During Health Examination. ...the test was performed after the President made an 'informed patient request'. ...the commander-in-chief felt it was important enough to ask for the test personally."  Read more here.