Imaging
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DIAGNOSTIC IMAGING

When you are diagnosed with prostate cancer (or any cancer) you want to know where the cancer is and if it can be completely eradicated by the recommended treatment. Unfortunately, cancer can spread outside the prostate by growing through the capsule into the periprostatic tissue and seminal vesicles or by cells entering the lymph system or the blood vessels. These cells may be lodge in the lymph nodes (near or distant), bone marrow, lungs or other locations. The cells may be attacked by the immune system. They may fail to survive outside the prostate. Or, they may multiply to form new tumors.

Imaging tests may help to determine whether the cancer is still confined to the prostate or has spread elsewhere but they usually require a significant tumor mass. Many technologies require about one cubic centimeter of tumor that is around one billion cells. Therefore, imaging studies are often not recommended for newly diagnosed, low-risk men because the probability of identifying a significant tumor mass is extremely low. See the Risk Assessment subsection.

If you do have imaging tests, you should get a copy of the written report by the Radiologist and obtain CD-ROM copies of all scans that can be taken to future Radiologists for comparison with new scans.

 

Bone Scan

A radionuclide bone scan uses a radioactive tracer to look at the inside of the bones. A small amount of tracer is injected into a patient’s vein. It collects in areas of the bone and is detected by a special, gamma camera. Healthy bone appears gray to the camera, and areas of injury, such as those caused by cancer, appear dark. These places could be rapid bone growth resulting from cancer, or they could be caused by arthritis, prior injuries or other bone diseases. To find out if cancer is present, more tests (x-ray, MRI, CT or bone biopsy) may need to be done. The tracer soon passes out of the body via the kidneys (which normally show on the scan).

It is considered a standard of care to omit the bone scan in patients with newly diagnosed men with low-risk disease.

Learn What to expect during a bone scan.

 

Computed Tomography (CT or CAT) Scan

A CT scan creates a three-dimensional picture of the inside of the body with a special type of x-ray machine that takes many cross-sectional images. A computer then combines these images into a detailed view that shows any abnormalities or tumors. Sometimes, a contrast medium (a special dye) is injected into a patient’s vein to provide better detail. A CT scan can help tell if your prostate cancer has spread into lymph nodes in your pelvis. CT scans are not as useful as MRIs for looking at the prostate gland itself.

A pelvic CT scan may be omitted in patients with newly diagnosed, low risk prostate cancer.

Learn What to expect during a CT scan.

 

Color Doppler Ultrasound (CDU)

A prostate biopsy is normally done with “relatively” low-resolution ultrasound equipment. The objective being, to accurately view the shape of the prostate for random placement of the biopsy needles into the prostate zones. Power color Doppler ultrasound demonstrates blood flow inside the prostate. Usually, cancer tissue shows a higher blood flow pattern than that of normal tissue. This capability can improve detection and actual tumor size measurement.

Nelson, et al [1] reported: “Abnormal color flow was strongly associated with Gleason score 8 to 10 lesions but not with lower-grade lesions.”

CDU is especially valuable for men with continual rising PSA and successive negative random biopsies. It is also very useful for assessing extracapsular extension and in monitoring prostate cancer for men diagnosed with prostate cancer who are pursuing active surveillance. Unfortunately, there are few physicians who use power color Doppler ultrasound for prostate cancer diagnosis and staging. Contact the PCRI Helpline for the ones we are aware of. For more information, see our article:
Color Doppler and Tissue Harmonic Ultrasound

1 – Nelson ED, Slotoroff CB, Gomella LG, Halpern EJ.. Targeted biopsy of the prostate: the impact of color Doppler imaging and elastography on prostate cancer detection and Gleason score. Urology 2007 Dec;70(6):1136-40

 

Magnetic Resonance Imaging (MRI)

Magnetic resonance imaging (MRI) uses radio waves and strong magnets, not x-rays, to produce detailed images of the body. The MRI may give a very clear picture to help the doctor see whether the cancer has spread to the seminal vesicles or the bladder.  A contrast medium may be injected into a patient’s vein to create a clearer picture.

Learn What to expect during an MRI.

In a PCRI Insights article, Dr. Barentz stated: “Functional multi-modality MR imaging includes high resolution MR imaging, dynamic contrast-enhanced (DCE) MRI, MR-spectroscopy (MRS), and diffusion weighted MR imaging (DWI). With functional multi-modality MR imaging, it is possible to detect and exactly localize the tumor in the prostate with more than 90% accuracy. DCE-MRI gives more information regarding the perfusion of the prostate and the tumor”.

See our articles: MRI in Prostate Cancer and Prostate MRI: Information for Patients

 

Endorectal MRI with spectroscopy

Magnetic resonance images, especially high spatial-resolution, endorectal coil MR images, provide an excellent depiction of prostatic anatomy with regions of healthy prostate tissue demonstrating higher signal intensity than prostate cancer. This reduction in MR image signal intensity is due to a loss of the normal glandular (ductal) morphology in regions of prostate cancer. However, other benign pathologies (e.g. inflammation, stromal BPH) and therapy also cause a loss of ductal morphology and low signal intensity on MRI. Additionally, infiltrating prostate cancer may not cause a reduction in normal glandular morphology and therefore will not be hypointense on MRI. Due to these confounding factors, MRI alone has demonstrated good (78%) sensitivity (few false negatives) but poor (55%) specificity (many false positives) in detecting cancer in the prostate.

Performed in conjunction with high-resolution anatomic imaging (MRI), Magnetic Resonance Spectroscopic Imaging (MRSI) provides a non-invasive method of detecting small molecular markers (choline containing metabolites, polyamines and citrate) within the prostate. On MRSI spectra, the resonances for choline, creatine, polyamines and citrate occur at distinct frequencies. The areas under these signals are related to the concentration of the respective metabolites, and changes in these concentrations can be used to improve specificity for identifying cancer.

An MR-examination, performed at high field strength (3 Tesla) with use of an endorectal coil (ERC), allows a very accurate determination of minimal (sub-millimeter) extraprostatic spread. The sensitivity and specificity of 3T ERC MR imaging for determination of extraprostatic disease are respectively 87% and 96%

See our articles:
Magnetic Resonance Anatomic and Spectroscopic Imaging of Prostate Cancer – Current Status
Endorectal MRI with spectroscopy – 2000

Endorectal-MRI + Spectroscopy may be beneficial to stage prostate cancer locally and evaluate ECE (extra-capsular extension), SV (seminal vesicle involvement) or regional nodes. Prostate MRI is a developing field and quality results are much more likely when the imaging is done at a center of excellence. This diagnostic technique was pioneered at UC San Francisco and Memorial Sloan Kettering in New York City. These and other possible locations may be found on the ProstateMR.org website.

 

Positron Emission Tomography (PET) Scan

A PET scan is a way to create pictures depicting the biochemical processes such as glucose metabolism inside the body. A small amount of a radioactive substance is injected into a patient’s body and absorbed by the organs or tissues being studied. This substance gives off energy that is detected by a scanner, which produces the images. PET scans have used a radioactive tracer called fluorine-2-D-deoxyglucose (FDG). This has not proven very useful for prostate cancers which typically have a low-rate of glucose absorption. Other tracers are being investigated that appear to be more useful including: 18F-Fluorocholine (FCH), Carbon 11 Acetate, 18F-Dihydro-Testosterone, C-11 choline, etc. Find out What to expect during a PET scan or an Integrated PET-CT scan.

 

x-rays

Diagnostic X-ray (radiography) is an examination using electromagnetic energy beams to produce images onto film or computer.  While not used for initial evaluation of prostate cancer, x-rays may be requested to evaluate suspicious findings on bone scans to distinguish between former injuries, arthritis or metastatic cancer. They could also help to rule out lytic bone disease that would be missed on bone scan and which may be present given the high Gleason score presentation. Such x-rays would be taken of the hip joints and pelvis. For additional description see: Bone X-ray

 

ProstaScint scan

Like the bone scan, the ProstaScint scan uses low levels of a radioactive substance to find cancer that has spread beyond the prostate. ProstaScint (Indium-111 capromab pendetide) imaging uses a SPECT gamma camera for detecting prostate cancer. This is usually done about half an hour after the injection and again 3 to 5 days later. ProstaScint is a site-specific murine monoclonal antibody that is reactive with prostate specific membrane antigen (PSMA), a glycoprotein expressed by prostate tissue. It is strongly reactive with both primary and metastatic prostate cancer in addition to normal prostate tissue. PSMA continues to be expressed in patients with androgen deprivation therapy, but is preferentially elevated with metastatic, poorly differentiated, and hormonally refractory prostate cancer, all situations in which PSA may not be useful.

ProstaScint received Food and Drug Administration (FDA) approval in 1996 for use as an imaging agent (1) for the staging of newly diagnosed patients with biopsy-proven prostate cancer who are at a high risk for soft tissue metastases or (2) for the restaging of post-prostatectomy patients with a rising PSA level.

ProstaScint Fusion imaging can significantly enhance detection of nodal disease, eliminate some of the false positive results from bowel activity, and accurately map the prostate gland for tumor distribution. Fusion imaging combines ProstaScint imaging with CT or MRI imaging and co-registers the images to provide improved diagnostic quality.

This test is not used frequently because there are a large number of false positives. Newer monoclonal antibodies may make this technology more useful in the future.

Learn more including Update on ProstaScint 

Combidex scan

Combidex (ferumoxtran-10) consists of iron-oxide containing nanoparticles. When this contrast agent is administered intravenously, it is taken up by macrophages and transported to healthy lymph tissue. The iron causes changes in the magnetic characteristics of the tissue that result in low signal intensity on MR images. Therefore, 24 to 36 hours after Combidex injection, healthy lymph nodes are black on MR images due to the iron within macrophages. Macrophages are absent in lymph nodes with metastasis, and thus these lymph nodes do not have a low signal: the tissue appears white. With Combidex, it is possible to examine the entire abdomen instead of only a restricted area surrounding a few pelvic blood vessels, as is the case with pelvic lymph node dissection. The diagnostic accuracy in the detection of lymph node metastasis is significantly higher than with CT scan.

Combidex, while promising, is not currently approved in the USA and is no longer available in the Netherlands. AMAG Pharmaceuticals discontinued the manufacture of Ferumoxtran-10 in 2010. They are pursuing approval of ferumoxytol as a replacement MRI agent. Watch for available clinical trials.

See our articles:
MRI in Prostate Cancer
Ferumoxtran-10 (Combidex): An Important New Prostate Cancer Staging Tool