Doctor's Blog

January, 2010

Prostate Cancer Screening

Prostate is second only to lung in cancer related deaths amongst American men. In 2009, there were 192,000 newly diagnosed cases and a predicted 29,000 deaths. The lifetime risk of developing prostate cancer is 1 in 6, but the risk of dying is only 2.9 %. This is because prostate cancer is usually a slow growing tumor. In an autopsy series of men who died of various causes, 1/3 under the age of 80 and 2/3 who were older had biopsy proven evidence of prostate cancer.

Risk factors for developing prostate cancer include age, race and family history. Rarely is it seen before the age of 40 years. Having a father or brother with prostate cancer increases a man’s risk by 2 fold, and having a father and a brother with prostate cancer increases the risk by four fold. African American men have the highest risk of developing and dying of prostate cancer, for reasons unknown.

Prostate-Specific Antigen (PSA) is widely used for cancer screening. Elevated levels are found in men with prostate cancer, but also in nonmalignant disease such as benign prostatic hypertrophy, prostatitis, trauma or prostate related surgery. Traditionally, screening has been done with digital rectal exam (DRE), but recent evidence has shown that it may not be sensitive enough to be used as a sole screening tool.

A PSA level of 4 ng/mL has been the most accepted cutoff. PSA levels between 4 and 10 are predictive of prostate cancer in only about 25% of cases and 75% of those are organ confined and potentially curable. Using a cutoff of 10 increases the predictive value to 42-64%, but lowers the sensitivity of the test. Too sensitive a threshold would subject patient to unnecessary and potentially harmful testing.

The PSA screening tool was recently evaluated by two large trials published in 2009 with conflicting results. The European Randomized Study of Screening for Prostate Cancer (ERSPC) reported screening decreased the risk of death by 20%. However, 48 additional patients would need aggressive treatment to prevent one death. The Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial, found no benefit for annual PSA and digital rectal examination (DRE) screening.

PSA velocity, PSA density, free PSA, and using age- and race-specific reference ranges have been proposed to improve the diagnostic performance of PSA, but currently there is no consensus on their use. Also, none of them has been shown to reduce the number of unnecessary biopsies or improve clinical outcomes.

In the area of cancer prevention, various studies have shown that neither vitamin e nor selenium protect against developing prostate cancer. However, finasteride and dutasteride have been shown to lower PSA levels and reduce the risk of developing prostate cancer by about 25 percent.

Prostate cancer screening using both DRE and PSA should be conducted in all men at risk of developing prostate cancer, and continue till the individual has a life expectancy of 10years. All along, the patient and clinician should have a dialogue to discuss the risk and benefits of screening and further testing.

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