Diagnostic Tests for Prostate Cancer
Prostate Biopsy and Ultrasound of the Prostate:
A urologist's recommendation for prostate biopsy depends on a number of factors including the digital rectal exam, total PSA level, percent Free PSA, age based PSA, and PSA velocity.
Transrectal Ultrasound Biopsy of the Prostate
The most common technique for prostate biopsy is called Transrectal Ultrasound Guided Needle Prostate Biopsy (TRUS/PNbx). An ultrasound probe is placed in the rectum. Prostate is examined in different dimensions. Suspicious areas are identified. A biopsy needle is passed through the ultrasound probe into various locations of the prostate. Multiple samples are obtained. The number of samples and the locations of biopsy are hot topics of discussion in the urologic literature. In general six to 18 samples are obtained from the outer edges of the prostate, as well as suspicious areas found on digital rectal exam or ultrasound exam.
A prostate Doppler exam is a trans-rectal ultrasound test of the prostate which uses sound waves to determine degree of blood flow in various regions of the prostate. The theory is that areas with higher blood flow contain cancerous lesions, an association which has not yet been proven. Research on this topic has not yet proven that an ultrasound Doppler of the prostate can accurately
find areas of cancer in the prostate.
Radiologic tests for prostate cancer
CT Scan (AKA "CAT SCAN"):
X-Ray test using radiation and intravenous contrast:
- Determine if there has been any metastasis to other organs or lymph nodes
- Determine if there is extension of prostate cancer beyond the capsule
MRI: Magnetic Resonance Imaging:
Film obtained by magnetic field without need for radiation. MRI is useful test for examining soft tissue and bones.
- Endo-Rectal Coil: Placement of probe within rectum to determine extension beyond capsule of prostate.
- Determine lymph node or boney involvement
X-Ray test using a radionuclide for bones to determine spread of cancer to bones
X-Ray test with radionuclide that attaches to tissues that make PSA. Theoretically if there is PSA production in an area outside the prostate gland, then that area probably contains prostate cancer, indicating prostate cancer spread. Prostascint Scan however is not very accurate, and has a high rate of false positive results.
Doppler exam is a trans-rectal ultrasound test of the prostate which uses sound waves to determine degree of blood flow in various regions of the prostate. The theory is that areas with higher blood flow contain cancerous lesions, an association which has not yet been proven. Research on this topic has not yet proven that Doppler of the prostate can accurately find areas of cancer in the prostate.
PET Scan: Positive Emission Tomography
PET Scan uses a radionuclide that looks for cells that are rapidly dividing and growing. Rapidly dividing cells usually represent cancerous cells. Therefore, PET Scan can be used to determine if there is metastasis outside the organ from which cancer originated. However, because prostate cancer cells do not divide and grow very fast, PET Scan is not an accurate test for prostate cancer.