New Screening Method May Help Diagnose Undetectable Prostate Cancer
Men with persistently increased or fluctuating prostate specific antigen (PSA) levels and a negative prostate biopsy may benefit from a new prostate cancer screening method that uses the combination of a novel drug therapy plus changes in PSA levels over time to identify men who are more likely to have aggressive prostate cancer.
Each year in the United States, more than 192,000 men are diagnosed with prostate cancer and more than 27,000 die of the disease. In the U.S., men older than 50 are often offered PSA testing for the early detection of prostate cancer. The PSA test measures proteins that are produced and shed by the prostate. PSA levels tend to be elevated when prostate cancer is present, but levels can also be elevated in benign (non-cancerous) conditions affecting the prostate. There has been some controversy surrounding screening for prostate cancer with the PSA test because it may identify some cancers that don’t require treatment, resulting in overdiagnosis and exposing some men to unnecessary treatment and complications.
Researchers from the NewYork-Presbyterian Hospital/Weill Cornell Medical Center have found that PSA can be a more effective marker for prostate cancer when used with an additional drug therapy rather than as a stand-alone test. They developed and tested a combination screening method that involves the use of two 5-alpha-reductase inhibitor drugs, which are designed to reduce the size of an enlarged prostate (finasteride and dutasteride) along with continued PSA testing to identify hard-to-detect prostate cancers.
The screening method is designed for men who have consistently abnormal PSA results despite negative biopsies. This patient population presents a challenge because PSA alone is not a good indicator of prostate cancer. The theory is that the drug therapy could improve the value of the PSA test—because if PSA levels remain high after the prostate has shrunk, it could indicate the presence of cancer. What’s more, when the prostate gland is smaller, biopsy can be more effective.
To evaluate the new method, researchers conducted a two-part study that included 276 men with a PSA of 4 or higher, a normal digital rectal examination, and two or more negative biopsies. During the first phase of the study, 97 patients received 5 milligrams of finasteride or dutasteride daily. These men underwent PSA testing at 6 and 12 months and a transrectal ultrasonography and a biopsy at one year. The results indicated that after one year of the drug therapy, PSA levels dropped by an average of 48 percent in all men; however, the level of reduction was significantly higher in men with benign prostate disease and significantly lower in the 28 percent of men whose prostate biopsy detected cancer.
During the second phase of the study, 179 patients received the same drug therapy but only underwent biopsy if their PSA showed a change of more than 0.4 ng/ml. Overall, 42 men underwent biopsy and 26 of those men had cancer. Among those that had cancer, 77 percent had high-grade tumors.
The researchers concluded that the level of change in PSA levels after 5-alpha-reductase inhibitor therapy may be useful in diagnosing prostate cancer in patients with persistently high PSA levels and negative biopsies. What’s more, the screening method may prevent unnecessary biopsies. The researchers speculated that the drug therapy may be helpful in diagnosing undetectable prostate cancer.
Kaplan SA, Lee RK, Chung DE, et al. Prostate biopsy in response to a change in nadir prostate specific antigen of 0.4 ng/ml after treatment with 5α-reductase inhibitors markedly enhances the detection rate of prostate cancer. Journal of Urology. 2012; 188(3): 757-761.
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