What Diagnostic Tests And Procedures Are Used For Prostate Exams?
There are a variety of different screening options, diagnostic tests, imaging techniques and procedures that can be used to determine if an individual has prostate cancer and how far their prostate cancer may have spread, if at all. An overview of some of the most common diagnostic tests and procedures are highlighted below. Your doctor will help you determine which, if any, of these options you may need, and how to prepare for them. Not all diagnostic measures can provide a completely clear idea of what an individual’s cancer may look like, so oftentimes, many of these are used in combination with one another.
A common method used to screen for the possibility of prostate cancer is the PSA test. PSA, or prostate-specific antigen, is a protein made by normal prostate cancer cells and cancerous cells in the prostate. When a man’s PSA level is higher than usual, it could be indicative of prostate cancer. The PSA test is not used as a diagnostic procedure, but can be used in combination with other screening methods, such as the digital rectal exam (DRE), to alert your provider of a potential problem. If your doctor suspects that you may have prostate cancer, they may recommend more invasive screening or diagnostic measures such as a transrectal ultrasound, a prostate biopsy, or other imaging techniques like MRIs or CT scans.
The definition of a normal PSA level may vary based on a variety of different factors. PSA levels are often measured in ng/mL (nanograms of PSA per milliliter of blood). Typically, a result of 4 ng/mL or lower (sometimes referred to as a PSA level of 4), is considered normal, however, your doctor may want to pursue additional screening even at lower levels if you’re at an increased risk of developing prostate cancer based on your family history, race, or other behaviors such as smoking.1-4
A transrectal ultrasound, also known as TRUS, is an imaging technique used to help diagnose prostate cancer and other potential problems within the prostate. TRUS can be used on its own, or to guide needles taking tissue samples from the prostate during a biopsy. TRUS can also be used to guide other treatments including brachytherapy (internal radiation) and cryotherapy.
Ultrasounds, including transrectal ultrasounds, rely on high frequency sound waves. These sound waves are emitted from a transducer, or a probe, and bounce off of structures within the body. The probe is connected to a computer that will generate real time images of bodily structures based on how the sound waves behave. These images can be used to investigate nodules (or bumps) found during a digital rectal exam, as well as to investigate the prostate gland further after a high PSA (prostate-specific antigen) test result. TRUS can also evaluate the size of the prostate gland, and the state of nearby organs to help diagnose other non-cancerous conditions, such as benign prostatic hyperplasia (BPH), that may contribute to symptoms such as difficulty urinating.5,6
A biopsy is a sample of tissue taken from the body that is analyzed further to detect certain conditions, including cancer. For prostate cancer, there are two main types of biopsies, core needle biopsy and lymph node biopsy.
Core needle biopsy with ultrasound guidance
A core needle biopsy is biopsy used for prostate cancer detection. If your doctor suspects that you may have prostate cancer based on earlier detection methods, they may recommend you undergo a core needle biopsy. Core needle biopsies involve inserting thin, hollow needles into the prostate gland to collect tissue samples called cores. The needles can be inserted into the prostate through the wall of the rectum. This is called a transrectal core needle biopsy.
The needles utilize a special spring-loaded technology to insert and remove the needle, with the tissue sample, in under a fraction of a second. Ultrasound guidance (TRUS) can be used to guide the needles into different areas of the prostate. This process will be repeated roughly 10-12 times to collect the samples. These samples will be analyzed under a microscope to look for the presence of cancerous cells.5,6
Pelvic 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. If the cancer has spread beyond the prostate and into the local lymph nodes, a radical prostatectomy will often no longer be effective and can be avoided. In addition to happening during surgery to stop a potentially unnecessary procedure, a lymph node biopsy can also be completed on its own using a laparoscopic approach or fine needle aspiration to remove a small sample of pelvic lymph node tissue.5,7
Tests 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 tests for cancer spread include:
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.5,8
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). When PET-CT scans are analyzed, the areas of the body that absorb the radioactive tracer will stand out.5,9
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.5
This is not an exhaustive list of all diagnostic tests and procedures, and the ones listed may be utilized for other purposes than just what is stated above. It is important to remember that diagnosing and accurately characterizing a case of prostate cancer and its potential spread can often be a complex process that requires many different techniques and efforts. Your health care team will help you determine which options are best for you, and how you can prepare for them.