Prostate cancer develops in the prostate, a small gland in the male reproductive system. This gland produces fluid that mixes with semen. While many prostate cancers grow slowly and may not spread, some can be more aggressive. When cancer cells break away from the original tumor and travel to other parts of the body, it is known as metastasis.
Initial Locations of Spread
Prostate cancer cells can spread from the prostate through the lymphatic system or the bloodstream. The initial sites where prostate cancer most commonly spreads are the lymph nodes and the bones.
Lymph nodes are small, bean-shaped glands that are part of the body’s immune system. Due to their proximity to the prostate, the lymph nodes in the pelvic area are often the first to be affected when prostate cancer spreads. Cancer cells can enter these nodes, preventing them from draining fluid effectively, which may lead to swelling.
Bones are a common initial site for prostate cancer to spread, particularly the spine, pelvis, ribs, and femurs. Over 60% of individuals with advanced prostate cancer experience spread to the bones. This occurs because cancer cells can travel through the bloodstream and find a suitable environment for growth within the rich blood supply of bone tissue. The spine, especially the lower back, is the most frequently affected bone, followed by the hips and pelvis.
Beyond the First Sites
While lymph nodes and bones are common initial sites, prostate cancer can spread to other organs as it progresses. These less common, but still significant, sites include the lungs, liver, and, rarely, the brain.
Cancer cells can reach the lungs by traveling through the bloodstream. While lung metastasis may not always cause noticeable symptoms in early stages, it can impact lung function as it advances.
The liver can also become a site for prostate cancer metastasis. Liver metastases may not present with clear symptoms in their early stages, making them challenging to detect until they are more advanced.
Brain metastases from prostate cancer are less common compared to other sites. They tend to occur in advanced stages of the disease.
Recognizing Signs of Metastasis
When prostate cancer spreads, it can cause various symptoms depending on the affected area. Recognizing these signs can prompt timely medical evaluation, although these symptoms can also be caused by other conditions.
If cancer has spread to the lymph nodes, individuals might experience swelling in the legs or groin, often accompanied by discomfort. This swelling, known as lymphedema, results from fluid buildup when lymph nodes are unable to drain properly.
Bone metastasis commonly causes pain, which can be persistent and may worsen at night. This pain can range from a dull ache to a sharp, stabbing sensation. Bones affected by cancer may also become weaker and more prone to fractures with minimal trauma. If the spine is involved, there can be weakness or numbness in the legs, and in severe cases, spinal cord compression, which is a medical emergency.
Symptoms of lung metastasis can include a persistent cough, shortness of breath, or chest pain. In some instances, individuals may cough up blood or experience a buildup of fluid around the lungs.
If the liver is affected, symptoms may include discomfort or pain on the right side of the abdomen, nausea, poor appetite, and unexplained weight loss. A swollen abdomen (ascites) and yellowing of the skin and whites of the eyes (jaundice) can also occur.
Brain metastases, though rare, can manifest as headaches, seizures, changes in thinking or memory, or vision problems. Patients may also experience weakness or numbness in the limbs.
Diagnosing Spread
Healthcare professionals use several methods to determine if prostate cancer has spread beyond the prostate. These diagnostic tools help identify the location and extent of metastasis.
Blood tests, such as the prostate-specific antigen (PSA) test, are routinely used to monitor prostate cancer. While PSA levels can indicate the presence of cancer, they are not diagnostic of spread alone. However, a rising or rapidly increasing PSA level, despite treatment, can suggest that the cancer is metastasizing. Blood tests can also assess if the cancer is affecting organs like the liver or kidneys.
Imaging tests are crucial for detecting metastasis. Bone scans are frequently used to identify if cancer cells have spread to the bones, as these areas will absorb a radioactive tracer differently. Computerized tomography (CT) scans use X-rays to create detailed cross-sectional images, helping to detect spread to lymph nodes or other organs like the liver or intestines. Magnetic resonance imaging (MRI) uses magnetic fields and radio waves to produce detailed pictures of soft tissues and can detect spread to lymph nodes or bone marrow. Newer imaging techniques, such as PET scans, especially those using specific tracers like PSMA, can also detect prostate cancer spread to various parts of the body.
A biopsy of a suspected metastatic site may be performed to confirm the presence of cancer cells. This involves taking a tissue sample from the affected area for microscopic examination.