Diagnosing prostate cancer continues to present a challenge, and relies largely on the results of a biopsy. The decision to do a biopsy is based mainly on an elevated PSA or abnormal digital rectal exam (DRE). But we know that most patients with elevated PSAs won’t end up being diagnosed with prostate cancer. Progress has been made in techniques such as ultrasound and magnetic resonance imaging (MRI), but it’s almost impossible to rely on radiologic tests for diagnosis. Huge efforts are going into improving MRI, but at present this type of exam seems more appropriate for evaluating the extent of the cancer after diagnosis than for making the actual diagnosis.
Among the tests available to improve cancer detection and minimize the need for biopsy, the ratio of free to total PSA, which enhances the performance of PSA testing, is the most used.
Another tool now at our disposal is a test that measures the amount of PCA3 (prostate cancer gene 3) in a urine sample. PCA3 is found only in prostate cancer cells (not in other types of cancer); the quantity of PCA3 in cancerous cells is greater than that in normal prostate cells. Like the free/total PSA ratio, it doesn’t confirm the presence of cancer in the prostate, but rather helps identify men who should undergo further evaluation. The higher the PCA3 value, the greater the risk of cancer.
The PCA3 test shows a benefit in these situations:
- To identify new prostate cancers (to help decide if a biopsy is justified)
- To identify those who should have a repeat biopsy (for men whose PSA is progressively rising)
- After a diagnosis, to identify candidates for active surveillance
More and more, biopsies detect prostate cancers that are considered nonsignificant. Men may then be offered a program of active surveillance until such time as the cancer is seen to progress. But how to be certain that a cancer is truly insignificant? Studies have suggested that the PCA3 value is directly related to the presence of high-grade cancer or a significant volume of cancer. Thus it’s possible that this urine test may help point out good candidates for active surveillance, and at the same time help us avoid not treating men whose biopsies might have underestimated the extent of their cancers. It’s important to remember that these findings are preliminary and must be confirmed in larger studies.
The PCA3 test seems promising. Its value lies in providing additional information that you and your doctor can integrate into decision-making; it doesn’t, unfortunately, verify the presence of cancer or its aggressiveness.
The PCA3 test is still a sophisticated test requiring analysis in private laboratories, outside of most hospital settings. While the test isn’t covered by provincial health programs, most private insurance plans will reimburse the cost.
