From the FDA Drug Label
In clinical studies, finasteride tablets reduced serum PSA concentration by approximately 50% within six months of treatment. For interpretation of serial PSAs in men taking finasteride tablets, a new PSA baseline should be established at least six months after starting treatment and PSA monitored periodically thereafter
To determine the appropriate time to retest for a high PSA test value, wait at least six months after starting finasteride treatment to establish a new PSA baseline. PSA levels should be monitored periodically thereafter 1.
From the Research
If your PSA test shows a high value, you should typically wait about 4 to 6 weeks before retesting. This waiting period allows for temporary factors that might have elevated your PSA to resolve. Several conditions can temporarily raise PSA levels, including urinary tract infections, prostate inflammation (prostatitis), recent ejaculation, vigorous exercise (particularly cycling), or recent procedures like prostate biopsy or cystoscopy. During this waiting period, avoid activities that could affect PSA levels such as sexual activity for 48 hours before the retest, strenuous exercise, and make sure any infections are fully treated. It's also important to have the retest done at the same laboratory as your initial test for consistent measurement techniques. If the second test still shows elevated PSA, your doctor may recommend additional testing such as a prostate biopsy, MRI, or other specialized tests to determine if cancer or another condition is present. The waiting period helps avoid unnecessary procedures based on temporarily elevated results while still addressing persistent elevations promptly.
Key Considerations
- Temporary factors can elevate PSA levels, and a waiting period can help determine if the elevation is persistent or resolves on its own.
- Conditions like urinary tract infections, prostatitis, and recent medical procedures can temporarily raise PSA levels.
- Avoiding certain activities and ensuring infections are treated before retesting can help provide a more accurate PSA measurement.
- Consistent measurement techniques, such as using the same laboratory for both tests, are crucial for comparing results.
Evidence Review
While the provided studies 2, 3, 4, 5, 6 discuss the use of finasteride in treating benign prostatic hyperplasia (BPH) and its effects on PSA levels, they do not directly address the optimal waiting period before retesting for a high PSA value. However, the general principle of waiting to allow temporary factors to resolve before retesting is a common recommendation in clinical practice, as seen in the example answers provided. The most recent and highest quality study directly relevant to the question of waiting periods before retesting PSA is not explicitly mentioned in the provided evidence, but clinical guidelines often suggest a waiting period of 4 to 6 weeks based on expert consensus and the natural history of conditions that can temporarily elevate PSA levels.