When Does Mesothelioma Metastasize?
Distant metastases occur in 10% to 50% of stage 4 mesothelioma cases. Cancer cells can spread locally, regionally and distantly.
In stages 1, 2 and 3, cancer cells spread locally within the bodily cavity where they developed and regionally to lymph nodes. Only in stage 4 can mesothelioma metastasize to distant parts of the body.
It is generally more common for mesothelioma to continue spreading throughout the cavity where it originally formed. This is known in the medical field as a local spread.
Cancer progression is detected through diagnostic imaging tests, which include MRIs, PET or CT scans. Doctors usually suspect that a cancer has spread when a patient complains of symptoms that are not generally associated with mesothelioma. At that time, tests or biopsies will be performed to look for distant metastases.
Where Does Mesothelioma Metastasize?
Mesothelioma most commonly metastasizes to the:
- Adrenal glands
Mesothelioma can spread throughout the body in a number of ways.
Metastasis generally occurs when cancer cells travel through the bloodstream or lymphatic system to distant sites. Once mesothelioma cells have spread around the body, they can invade organs and cause secondary tumors to develop.
Cancer cells reach the blood stream through angiogenesis, a process that forms new blood vessels in the body. Researchers are studying ways to promote and block angiogenesis to develop a number of anti-angiogenic medications. These treatments may be the key to slowing or halting the spread of cancer.
Drugs being evaluated for mesothelioma metastasis include semaxanib (SU5416), thalidomide and tetrathiomolybdate. In clinical trials, the three medications demonstrate an ability to help stabilize the disease and increase survival.
Metastatic Pleural Mesothelioma
For many years, doctors considered pleural mesothelioma a localized disease with limited ability to metastasize to other parts of the body. However, a 2012 postmortem study of 318 mesothelioma patients from Australia and England revealed that 55.4% of them had metastases to distant sites.
A similar review of 172 people who died of pleural mesothelioma found that the most common sites for mesothelioma metastasis include:
- Liver (55.9%)
- Adrenal glands (31.3%)
- Kidneys (30.1%)
- The opposite lung (26.8%)
Cancer spread to the brain and central nervous system is significantly rarer, occurring in only about 3% of postmortem cases.
In stage 4, pleural mesothelioma metastasizes to distant sites in more than 10% of cases.
By the time most people receive a mesothelioma diagnosis, their cancer is already in the later stages of development. If the cancer has spread to distant parts of the body, treatment options tend to be palliative in nature, meaning they aim to relieve symptoms and provide comfort rather than cure the disease.
Metastatic Peritoneal Mesothelioma
In its early stages, peritoneal mesothelioma generally does not spread beyond the peritoneal cavity, which contains the stomach, spleen, liver, intestines and other abdominal organs.
As the disease progresses, cancer cells spread to nearby organs and distant locations. About 50% of peritoneal mesothelioma cases have distant metastases found at autopsy.
The most frequent sites of peritoneal mesothelioma metastases include:
- Visceral peritoneal lining
- Abdominal lymph nodes
Less frequently it metastasizes to the:
- Adrenal glands
- Soft tissue
Metastatic Pericardial Mesothelioma
Local spread of pericardial mesothelioma usually involves the pleura, lung and mediastinum.
Pericardial mesothelioma metastasizes in about 25% to 45% of cases to regional lymph nodes, lungs and kidneys.
Metastatic Testicular Mesothelioma
As testicular mesothelioma progresses, it tends to spread from the tunica vaginalis to retroperitoneal lymph nodes followed by inguinal and iliac lymph nodes.
When it metastasizes, which is relatively rare, it spreads to thoracic and lumbar vertebrae, omentum, liver and lungs.
What Other Factors Influence Metastasis?
Doctors use mesothelioma staging system to help gauge the progression of mesothelioma. Patients diagnosed with mesothelioma at stage 1 or stage 2 have the least risk of metastasis and the best prognosis, living around two to three years.
Patients diagnosed with mesothelioma at stage 3 or stage 4 are the most at risk of metastasis and may already have distant metastases. This is the most difficult stage to treat because the cancer is spreading into vital organs. At this stage of development, treatment is limited to palliative, symptom-controlling care. This leads to a life expectancy of less than a year.
The rate at which cancer grows and spreads depends in part on the cellular makeup of the tumor. Tumors with an epithelial makeup are typically less aggressive and spread more slowly, adding time to life expectancy.
Sarcomatoid and biphasic mesotheliomas, on the other hand, spread more quickly to other areas of the body, minimizing treatment options and reducing expected life span.
Response to Treatment
Early-stage patients who respond well to aggressive treatment may have a reduced risk of developing metastatic mesothelioma.
Surgery can reduce the risk of metastasis by removing tumors and cancer cells that may have led to spreading. Chemotherapy and radiation therapy can delay or prevent metastasis, and so can a new class of drugs called anti-angiogenesis therapy.
Radiation therapy is particularly effective at preventing local recurrence and sometimes used to treat tumors that develop in the chest wall.
A new FDA-approved treatment for mesothelioma, known as Tumor Treating Fields, also delays or prevents mesothelioma metastasis.
What Are the Symptoms of Metastatic Mesothelioma?
It can be difficult for doctors to detect when mesothelioma has metastasized. Distant spread occurs late in the cancer’s development and doesn’t always cause noticeable symptoms.
If metastatic cancer symptoms do arise, they usually affect the location where the cancer has spread. However, some symptoms of mesothelioma metastases are no different from common symptoms of mesothelioma and other cancers. Doctors often discover metastases by chance after imaging scans or other tests.
Metastatic Liver Cancer
Mesothelioma cancer spread to the liver may cause:
- Abdominal pain or discomfort
- Swelling of the legs
Metastatic Adrenal Cancer
Mesothelioma cancer spread to the adrenal glands, located on the top of each kidney, may cause:
- Back pain
- Muscle weakness
- Abdominal pain or discomfort
- Weight loss
Metastatic Kidney Cancer
Mesothelioma cancer spread to the kidneys may cause:
- Pain in the side or back
- Lumps on the side or back
- Blood in urine
- High blood pressure
Metastatic Brain Cancer
Mesothelioma cancer spread to the brain can cause a variety of neurological symptoms, including:
- Poor coordination or clumsiness
- Memory loss
- Severe headaches
- Personality changes
- Vision changes
Metastatic Spleen Cancer
Mesothelioma cancer spread to the spleen is often asymptomatic, but may cause:
- Severe abdominal pain
- Rupture of the spleen
Treating Metastatic Mesothelioma
Once mesothelioma has metastasized, treatment will focus on controlling the cancer and its symptoms in addition to extending life span. Doctors often suggest palliative treatments that ease pain, improve quality of life and improve survival.
- Chemotherapy can delay metastasis, improve survival and reduce pulmonary symptoms.
- Radiation therapy can prevent local recurrence and treat painful chest wall metastases.
- Anti-angiogenesis drugs can slow or stop mesothelioma metastasis.
- Tumor Treating Fields can delay or prevent mesothelioma from spreading.
- Medications and physical therapies can treat pain caused by distant metastases.
An oncologist with experience in treating this aggressive asbestos-related disease will be able to recommend the best course of treatment for metastatic mesothelioma.
Clinical Trials Targeting Metastatic Spread
Many clinical research trials are publishing promising results for patients with metastatic mesothelioma. Specialists are utilizing emerging therapies such as immunotherapy and gene therapy to improve patient survival significantly.
Immunotherapy has become one of the most significant medical advances for the metastatic mesothelioma community. Researchers are focused on the potential benefits of this targeted therapy, which uses patients’ immune systems to combat mesothelioma.
Scientists are studying the possibility of manipulating patients’ genes to treat and prevent certain diseases. The goal of gene therapy is to repair problems caused by defective genes directly, which could slow the spread of metastatic disease.
Mesothelioma specialists have recently started combining traditional therapies with experimental treatments. Researchers are investigating the benefits of treating metastatic disease with novel therapies such as immunotherapy and gene therapy when combined with existing modalities, such as surgery and chemotherapy.
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