Except for skin cancer, prostate cancer is the most common cancer American men face. In 2014, approximately 233,000 new cases of prostate cancer will be diagnosed. Most cases of prostate cancer are diagnosed in men over age 65, and it is rare in men younger than 40. While prostate cancer can be serious, most men diagnosed with prostate cancer actually die from something else, because it tends to grow slowly.
Prostate cancer is classified into four stages that indicate how far the disease has spread. Stages I and II are early stage prostate cancer that has not spread outside the prostate. Stage II prostate cancer is more likely to spread beyond the prostate. Stages III and IV prostate cancer are cancers that have already spread to other parts of the body.
Staging of prostate cancer is done by testing of the tissue samples from the prostate. This is known as Gleason testing. Generally, doctors only use medical imaging tests for men whose Gleason score and levels of prostate-specific antigen (PSA) indicate that the cancer has spread. This typically means a Gleason score of 7 or greater, and a PSA level greater than 10 nanograms per milliliter of blood.
The main reasons medical imaging is not often used in early prostate cancer cases are:
• There is some risk from radiation exposure.
• Imaging tests can cause false positive results that can be needlessly stressful.
• Imaging tests may be expensive, and in many cases are not shown to be beneficial.
Traditional Radiography and Prostate Cancer
Traditional radiography (x-rays) cannot demonstrate localized prostate disease, and is generally only useful in evaluation of prostate cancer that has spread to other organs. In cases of advanced prostate cancer, skeletal radiography may help doctors distinguish metastatic cancer from degenerative bone conditions that may be present in older individuals. Sometimes chest x-rays are used in patients with prostate cancer that has spread in order to further evaluate their condition.
Ultrasonography and Prostate Cancer
Transrectal ultrasonography (TRUS) is a type of advanced medical imaging used in diagnosing, and sometimes in staging, prostate cancer. It is a readily available technology, is relatively inexpensive, and does not cause undue stress to the patient. But the sensitivity and specificity of TRUS are too low for screening purposes, so it is mostly used to measure prostate volume and to provide guidance for prostate biopsy.
When a doctor obtains samples of prostate tissue for biopsy, TRUS may be used to guide tissue sampling to regions where abnormalities have been found. Generally several “cores” or tissue samples are obtained, from several regions of the prostate. A physician may obtain anywhere from 10 to 40 cores, depending on the basis of the particular patient’s clinical features.
Computed Tomography and Prostate Cancer
Like traditional x-rays, computed tomography (CT) is of limited value in determining prostate pathology and in staging prostate cancer. But CT may be useful in detecting prostate cancer that has spread. For example, it may be used to detect metastases in lymph nodes or bones. CT scans are able to depict enlargement of the lymph nodes, and can provide good accuracy in evaluation of metastases to lymph nodes. The problem is, assessment of lymph node size is essential to lymph node staging, and CT cannot demonstrate cancer inside lymph nodes that are not enlarged. As for metastases to the bones, targeted CT scanning can be useful in diagnosing types of skeletal metastases called osteoblastic and osteolytic metastases.
Magnetic Resonance Imaging and Prostate Cancer
Magnetic resonance imaging (MRI) is a type of advanced medical imaging that may be used in prostate cancer patients for guiding prostate biopsy, staging of cancers that have been diagnosed through biopsy, planning of treatment, and post-treatment follow-up imaging. On MRI scans, most prostate cancers show up as low signal intensity areas within the high signal intensity normal tissue of the peripheral zone of the prostate gland. Around 70% of prostate cancers occur within the prostate’s peripheral zone, so MRI can be used to depict most prostate cancers. However, low signal intensity tumors in the central prostate gland may be indistinguishable on MRI from benign prostate enlargement.
MRI imaging can be very important in the assessment of local invasion of the seminal vesicle in prostate cancer patients without documented distant metastases. This may show up as an irregular bulging of the prostate outline, asymmetry of neurovascular bundles, or breach of the prostate capsule and infiltration of the fat surrounding the prostate. Spread of cancer to the seminal vesicle may be suspected in cases where there is abnormally low signal intensity in the lumen of the seminal vesicle, or where there is thickening of seminal vesicle walls.
Functional MRI, which visualizes changes in blood flow, is a type of advanced medical imaging that can increase the specificity and sensitivity of MRI in detecting prostate cancer. Functional MRI can visualize characteristics of tumors like particular cellular densities, development of new blood vessels, and tumor metabolism.
Another advanced medical imaging technique utilizing magnetic resonance is magnetic resonance spectroscopy, which provides information about the concentrations of certain cellular metabolites in the prostate like citrate and choline. Changes in these metabolites can help predict the presence of prostate cancer. Used in combination with MRI imaging, sensitivity and specificity of tumor detection is increased.
Positron Emission Tomography and Prostate Cancer
Positron emission tomography (PET) is a type of advanced medical imaging that has traditionally not been used for routine diagnosis of prostate cancer. Most cancers lend themselves to PET technology because they have increased glucose uptake that is readily imaged with PET scans. Prostate cancer, on the other hand, is a slow growing type of cancer that is less likely to show local glucose metabolism changes. However, nuclear medicine researchers are working on developing new radiotracers that could allow PET scans to be more useful in the visualization of metastatic prostate cancers, so its future in advanced medical imaging of the prostate may change.
SteleRAD is owned and operated by 23 radiologists with skill sets and experience that cover all radiological subspecialties, and their appropriate use in cases of prostate cancer. SteleRAD can help your medical facility by helping with a sudden increase in caseload, by filling in for physicians who are inaccessible or unavailable, or by providing a Board-certified second opinion. To learn more about SteleRAD’s radiology services, contact us online or call 954-358-5250.