Testing for Cancer Spread
Whether you’ve just been diagnosed with prostate cancer, are currently undergoing treatment, or have successfully completed treatment, there is always a chance that your prostate cancer can spread, or metastasize, to different parts of the body. This can happen before the cancer has even been detected for the first time, or can happen after treatment, in a process known as cancer recurrence. Regardless of when the cancer metastasis happens, once it has spread, it can become harder to treat. For this reason, it’s important to have tests to monitor for the possibility or extent of cancer metastasis, to determine the most efficient and directed cancer treatment.
Common testing procedures
The majority of tests involved in assessing a cancer’s spread involve imaging techniques, such as bone scans, MRIs, and CTs. Additionally, pelvic lymph node biopsies can be performed to determine if localized prostate cancer is spreading to local lymph nodes. The imaging tests often rely on magnetic fields, X-rays, radioactive materials, or even sound waves to create accurate and detailed photos of your body, including its soft tissues and other organs beyond the prostate.
Based on the results of screening tests including the PSA (prostate-specific antigen) test, the DRE (digital rectal exam), and information from any prostate biopsies (including Gleason score), your doctor will determine if you are at risk for cancer metastasis. Many men who are diagnosed early with non-aggressive cancer will not need to undergo tests for cancer spread, as the chances of this occurring are very slim.1
Preparing for tests
Before certain tests, you may need to stop eating or drinking for several hours before, receive an enema to empty your bowels, or receive injections of radioactive materials. Each test has its own set of requirements, and your doctor will let you know if there are any steps you need to take before or after your test. Some of these tests can be done in an outpatient clinic, including CT scans and MRIs, however, others, including lymph node biopsies and bone scans are often performed in a hospital or nuclear medicine facility.
Most results will be available in a few days, and your doctor will provide you with the most accurate timeline of when to expect news and how to interpret the results when them come. If you are anxious or concerned that too much time has passed since your test and you have no information, you can always contact your doctor’s office or the location where you had the test. Common tests for cancer spread include:
When cancer spreads, it may migrate to the bones. When cancer spreads to the bones, it destroys the bones, leading to areas of active cell turnover, including healthy bone cell death and cancerous tumor growth. During a bone scan, you will be injected with radioactive tracers (also called radionuclides) that will be attracted to these areas of high cell turnover. Once the radiotracers have had time to settle into these areas, a scan can be taken to determine where new tumors in the bones are.
This information can be used to determine if a cancer has spread or if a treatment option is working to shrink previously existing bone tumors. The areas where the radiotracers settle and light up on the scan are often referred to as hotspots. If a new hotspot appears, your doctor may need to use additional screening techniques like CT scans or MRIs to make sure the hotspot is in fact a new tumor.
The radiation given off from the tracers is very low, and the entire process is painless and done as an outpatient procedure (meaning you go home the same day). It may take up to 2-3 hours for the tracer to fully settle within the body, and the scan itself may take an additional hour. You also may be instructed to drink plenty of water during the whole process to flush out an extra amounts of tracer that do not get absorbed into the bones.2-4
CT scan/PET-CT scan
CT scans, also called CAT scans, or computed tomography scans, use many pencil-thin x-ray beams to create a comprehensive, cross-sectional image of an area of the body. This leads to a more precise and detailed image than a standard X-ray that only uses beams from one angle. CT scans can be used to determine if local lymph nodes are enlarged and may possibly be infiltrated with cancer or to see if cancer has recurred after treatment and is in organs or tissues around the prostate.
Similar to bone scans, CT scans can also use contrast material. A prime example of this comes from pairing PET scans with CT scans. A radioactive tracer is injected into the body that is taken up by cells that are in active turnover locations (similar to the areas of bone metastasis). Newer radioactive tracers have been approved for PET scans that bind to a protein found on the surface of prostate cancer cells. The proteins are called prostate-specific membrane antigen (PSMA). These tracers are often more effective at detecting cancer spread.
When PET-CT scans are analyzed, the areas of the body that absorb the radioactive tracer will stand out. This will allow areas of cancer growth to be pinpointed and the CT scan can provide high quality images of these locations. The tracer used in a PET-CT scan may take an hour to fully collect in the body, but the scan itself only takes 20-30 minutes.1,5
MRI, also known as nuclear magnetic resonance (NMR), MR, or magnetic resonance imaging, uses radio waves and strong magnets to produces images of the body, including organs and soft tissues. These images are similar to CT scans in that they are detailed, cross-sectional images taken from many different angles, but the way MRIs create this image is much different. MRIs detect signals from the hydrogen atoms in your body.
The information the magnets and radio waves receive from these atoms is used to create the final image. An image from an MRI is black and white, and can be used to look for signs of metastasis or to help plan treatment including surgery. MRIs can also produce an incredibly clear picture of the prostate gland and its surrounding structures, which can help determine if a case of prostate cancer has started to spread beyond the prostate.
A contrast called gadolinium can also be used with MRI to produce an even clearer picture of a specific structure in the body. Your doctor will let you know if your MRI will include contrast. While in the MRI machine, there will be lots of loud noises, and you will need to remain very still. You may be provided with earplugs or headphones with music to help drown out the noise and keep you relaxed. However, even with the best relaxation techniques, some individuals may feel panicked, anxious, or claustrophobic, as the metal machine can completely surround you depending on what area of the body is being scanned and your specific body size.
The MRI scan can take anywhere from 30 minutes to 2 hours. It is also important to tell your doctor or the technician running your scan if you have any metal in your body including pacemakers, aneurysm clips, screws, stents, tattoos, permanent makeup, or metal coils in your blood vessels.
For any of the above scans that are performed with contrast or tracers, it is possible to have a reaction to these materials. Your doctor will provide you with signs and symptoms to look for, and in many cases, you may will be monitored extensively throughout the procedure and even for an hour or more afterward.1,4,6
Lymph node biopsy
Lymph nodes play an important role in our immune system, as well as circulate fluid, nutrients, and more throughout our entire body. Cancerous cells can break off of a localized tumor in the prostate and infiltrate the pelvic lymph nodes, where they can then get into the lymph fluid. At this point, the cancerous cells begin to circulate around and can spread to other organs. During a lymph node biopsy, either an entire pelvic lymph node or a portion of a pelvic lymph node is removed from the body.
Lymph nodes can be removed during a scheduled radical prostatectomy to treat localized prostate cancer. In this instance, before the surgeon removes the prostate gland, they may remove a pelvic lymph node and have the sample frozen and analyzed on the spot before continuing with the operation. The reason for this is that radical prostatectomies (or the removal of the entire prostate gland) are often only effective for cases of prostate cancer that have not spread beyond the prostate gland.
If the lymph node tissue shows signs of cancer, there will rarely be a significant benefit to a radical prostatectomy, and the individual having their prostate gland removed may experience inconvenient, quality of life-altering side-effects that can be completely avoided.
In addition to its use during surgery to stop a potentially unnecessary procedure, a lymph node biopsy can also be completed on its own. This typically happens when a man is choosing not to have a radical prostatectomy in favor of radiation or other non-surgical treatment options. In these cases, parts of a pelvic lymph node may be taken out using a laparoscopic approach or fine needle aspiration (FNA).
In the laparoscopic approach, small incisions are made in the abdomen and tiny cameras and tools are inserted into the body to remove a small sample of tissue. FNA may be used if a lymph node (or multiple lymph nodes) appear large on a CT or MRI scan. Typically, CT images will be used to guide a hollow needle into the lower abdomen to take a small tissue sample from the lymph node in question. Both approaches have fast recovery times, leave small (if any) scars, and utilize anesthesia.1,7,8