A client is diagnosed with prostate cancer. Which test is used to monitor the progression of this disease?
A. Serum creatinine
B. Complete blood cell count (CBC)
C. Prostate-specific antigen (PSA)
D. Serum potassium
Correct Answer: C. Prostate-specific antigen (PSA)
The PSA test is used to monitor prostate cancer progression; higher PSA levels indicate a greater tumor burden. Elevated Prostate-Specific Antigen (PSA) levels (usually greater than 4 ng/ml) in the blood is how 80% of prostate cancers initially present even though elevated PSA levels alone correctly identify prostate cancer only about 25% to 30% of the time. We recommend at least 2 abnormal PSA levels or the presence of a palpable nodule on DRE to justify a biopsy and further investigation.
Option A: Serum creatinine levels may suggest blockage from an enlarged prostate. The percentage of free PSA in the blood can be a useful indicator of malignancy. If the total PSA is between 4 and 10 ng/ml, a free PSA percentage is considered valid. The free PSA percentage is calculated by multiplying the free PSA level by 100 and dividing by the total PSA value.
Option B: CBC is used to diagnose anemia and polycythemia. Prostate Cancer Antigen 3 (PCA3) is an RNA-based genetic test performed from a urine sample obtained immediately after a prostate massage. PCA3 is a long, non-coding RNA molecule that is overexpressed exclusively in prostatic malignancies. It is upregulated 66 fold in prostate cancers. If PCA3 is elevated, it suggests the presence of prostate cancer.
Option D: Serum potassium levels identify hypokalemia and hyperkalemia. PCA3 is best used to determine the need for a repeat biopsy after initial negative histology. Serial PCA3 testing may also be helpful in monitoring patients with low-grade prostate cancers on active surveillance.
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