Screening for Prostate Cancer Can Be Risky Business

BY MARK SCHOLZ

PSA Screening is Defensible and Essential

The majority of radical treatment decisions are made on the basis and results of PSA testing. PSA or Prostate-Specific Antigen, is a protein produced by cells of the prostate gland. The PSA test measures the level of PSA in the blood. Due to the dangers of overtreatment some experts have proposed forgoing PSA  testing altogether. However, this attitude is like throwing the baby out with the bathwater, since early diagnosis and treatment of high-grade prostate cancer unquestionably improves survival and quality of life.  

Too Many Biopsies and Too Much Treatment

In a perfect world the diagnostic process would detect all high-grade disease early and ignore all low-grade disease. Is such a goal attainable? The way things stand, it is unlikely. The present system relies on an immediate prostate biopsy when the PSA passes a specific threshold. Unfortunately, when cancer is diagnosed, regardless of the grade or risk level, immediate surgery or radiation usually follows.  

Primary Care MD’s to the Rescue

Primary care physicians can alter this landscape in two ways: First, by taking a more measured and insightful approach to selecting men for biopsy (see below). Second, by not delegating the treatment selection process to urologists after a biopsy shows cancer.  Urologists and radiation therapists do not always provide unbiased advice. An overview of how to select treatment has been published in a brochure available at the PCRI, entitled, Treatment for Newly-Diagnosed Prostate Cancer.

Estimating Risk of High-Grade Disease Starts with Prostate Size

PSA is only “normal” in relation to prostate size.  Prostate volume in cubic centimeters is measured with ultrasound or with MRI. A normal PSA  reading is one-tenth of the prostate volume.  Abnormal PSA is when the reading is 50% above normal.  For example, an abnormal PSA for a 30cc prostate is 4.5, for a 50cc prostate, it is 7.5 and for a 100cc prostate, 15 is considered abnormal. 

The PSA Test Is Not Perfect

Infections, lab errors and recent sexual activity can all cause an elevated PSA, If there is an infection, a course of antibiotics will bring the PSA down. However a false reading can be ruled out  with repeat testing.   Recently, a new urine test called PCA-3 became commercially available. Studies show that the amount of PCA-3 in the urine increases in proportion to both the size of the tumor and the aggressiveness of the cancer. Unlike PSA, PCA-3 is unaffected by the size of the prostate. 

Imaging

Prostate imaging with endorectal MRI or color Doppler ultrasound is improving rapidly. These imaging techniques are useful for measuring prostate size and for detecting high-grade prostate cancer. While imaging is not 100% reliable, studies indicate that larger amounts of high-grade cancer can be detected fairly consistently.  In situations where the need to do a biopsy is debatable, a high quality ultrasound or MRI study may provide additional assurance that a biopsy can be safely delayed. 

Look Carefully Before You Leap

Rather than rushing into a biopsy at the first sign of an elevated PSA, screening should be seen as diagnostic process combined with an ongoing dialogue with the patient. As information is gathered by repeat PSA testing, PCA-3 levels and prostate imaging, the likelihood of a biopsy diagnosing either low-grade or high-grade prostate cancer can be presented to the patient and compared with the risks of a biopsy.  

There are many mistaken fears about prostate cancer. These unwarranted concerns need to be addressed before diagnosis, before the word cancer becomes personal, and a man’s  capacity for rational thought is impaired.  

Most elderly men have prostate cancer and don’t know it.  And most are better off not knowing. Diagnosing low-grade prostate cancer can be a curse. Frightened patients are ill-prepared to navigate a powerful medical system predisposed to over-treatment. How bad is it? One New England Journal of Medicine study estimates that our system is so skewed that 48 men receive unnecessary treatment for each individual who truly benefits.