01. Mesothelioma Metastasis Overview
What Is Mesothelioma Metastasis?
Metastasis happens when cells break off of a primary tumor, travel somewhere else and form a new tumor. This may occur if tumor cells travel through blood vessels or the lymph system, which includes lymph nodes.
Experts say metastasis occurs in mesothelioma in steps, including:
- Mesothelioma cancer cells form in areas of normal tissue.
- Cancer cells travel into lymph nodes or blood vessels.
- Blood or lymph vessels carry the cancer cells away from their source.
- Cancer cells get stuck in small blood or lymph vessels.
- Cancer cells move into the tissue near their stopping point.
- Cancer cells grow in their new location until a secondary tumor forms.
- The secondary tumor sends signals to grow new blood vessels.
- The new blood vessels form and help the tumor keep growing.
These steps may happen over a long or short period of time.
Some patients may think that metastatic mesothelioma has limited treatment options. This may be because they assume cancer only progresses in late stages. But metastasis can occur even in early stages of mesothelioma. That means patients who have metastatic mesothelioma have almost as many treatment options as those who do not.
When Does Mesothelioma Metastasize?
Metastasis may occur at nearly any stage of mesothelioma. Metastasis that occurs far from the origin (distant metastasis) generally happens in stage 3 or stage 4 mesothelioma. Stage 4 mesothelioma may even be referred to as metastatic mesothelioma.
Patients may think metastatic mesothelioma has few treatment options and a poor prognosis, but this is not the case. Mesothelioma research has led to multiple effective treatment options for patients in later stages.
What Is the Prognosis for Metastatic Mesothelioma?
Stage 4 mesothelioma may be called metastatic mesothelioma. Life expectancy for later stages can depend on treatment approach and mesothelioma type. With treatment, mesothelioma prognosis for stages 3 and 4 ranges from about 12 to 26 months.
02. Metastasis Locations
Where Does Mesothelioma Metastasize?
Doctors may describe mesothelioma as being locally advanced or having distant metastasis.
- Locally advanced mesothelioma: The cancer has spread to areas near the primary tumor.
- Distant metastasis: The cancer has spread to areas far from the primary tumor.
Mesothelioma tumors often progress in areas near the primary tumor. Common sites of mesothelioma metastasis include lymph nodes and the linings of nearby organs.
For example, in pleural mesothelioma, the primary tumor develops in the lung lining. If the cancer is locally advanced, tumors may surround the affected lung. But the cancer may be contained to just the area near the original tumor.
If the original tumor spreads to the bones or liver, that is distant metastasis. According to research, distant metastasis of malignant mesothelioma is rare. But it may happen even before the cancer is locally advanced.
Patients interested in these concepts can talk about them with a mesothelioma doctor. Doctors can help patients understand how they may be affected by local or distant spread of cancer.
Metastatic Pleural Mesothelioma
Pleural mesothelioma commonly metastasizes to sites near the original tumor, including the lymph nodes and chest wall. It can also spread to more distant sites, like the brain or liver.
Metastatic Peritoneal Mesothelioma
Peritoneal mesothelioma commonly metastasizes to lymph nodes near the original tumor. It may also spread to nearby organs like the liver or kidneys.
Metastatic Pericardial Mesothelioma
Pericardial mesothelioma arises in the lining around the heart. It accounts for less than 1% of mesothelioma cases. This means information about pericardial mesothelioma metastasis is relatively sparse.
Available research shows pericardial mesothelioma metastasizes to nearby tissues like the lymph nodes and pleura. Case reports also indicate pericardial mesothelioma can spread to the following locations:
- Brain
- Liver
- Lung
- Nearby lymph nodes
- Pleura (the lining around the lungs)
Metastatic Testicular Mesothelioma
Testicular mesothelioma develops in the lining around the testis, the tunica vaginalis. It accounts for less than 1% of all mesothelioma cases. As such, little is known about testicular mesothelioma metastasis. Case reports indicate it may spread to the brain or spinal cord.
Resources for Mesothelioma Patients
03. Influencing Factors
Factors That Influence Mesothelioma Metastasis
Research has not yet determined what causes or encourages mesothelioma metastasis. But experts have suggested cell type and treatment may influence how mesothelioma cancer spreads.
Cell Type
Mesothelioma occurs in three main cell types: epithelioid, sarcomatoid and biphasic. It has been suggested that certain cell types spread faster than others. But medical literature is inconclusive about these claims.
There is no proof that certain cell types spread more quickly. But some studies suggest certain cell types may be more likely to spread than others. The studies do not agree on which cell type is more likely to spread, though.
- 2008 report: A study investigated lymph node metastasis in 53 pleural mesothelioma patients. Sarcomatoid and biphasic cell types had a higher rate of metastasis than epithelioid.
- 2020 report: A study investigated general metastasis in 164 pleural mesothelioma patients. Of the three cell types, epithelioid cells were more likely to spread to the abdominal lining than biphasic or sarcomatoid.
Additional mesothelioma research may help scientists learn more about cell types and metastasis.
Response to Treatment
Treatment success may have some influence on metastasis. For instance, if a given treatment kills every mesothelioma cell, there would be no cancer left to spread. A highly effective treatment could therefore prevent later metastasis of the original cancer.
On the other hand, if a given treatment leaves behind many mesothelioma cells, later metastasis may be possible. This concept may help explain why some treatments extend survival more effectively than others.
It may also help explain why earlier stages tend to have better survival. In earlier stages of mesothelioma, there may be less cancer to fight. This could hypothetically allow a treatment to kill a larger percentage of cancer cells. Fewer remaining cells might decrease the risk of later metastasis. The following studies demonstrate some of these concepts.
Early-Stage Pleural Mesothelioma Study
Pleural mesothelioma patients with little to no metastasis received chemotherapy followed by extrapleural pneumonectomy surgery. The study patients had a median progression-free survival of 16.5 months. Two patients lived at least three years without any evidence of metastasis or recurrence.
Late-Stage Pleural Mesothelioma Study
Researchers treated pleural mesothelioma patients with multimodal therapy. Nearly 90% of the study patients had stage 3 or 4 mesothelioma. They underwent surgery, photodynamic therapy and chemotherapy. This treatment kept mesothelioma from spreading or returning for about a year.
Does Mesothelioma Stage Affect Metastasis?
Mesothelioma stage does not necessarily affect metastasis. However, metastasis does impact stage.
Doctors determine a patient’s mesothelioma stage to help understand their prognosis and treatment options. Many physicians use some form of the TNM staging system to do this. The TNM system accounts for the number of tumors (T), lymph node spread (N) and distant metastasis (M). This means metastasis can strongly affect a patient’s stage at diagnosis.
Patients with more metastasis tend to have a higher stage of mesothelioma and vice versa.
04. Treating Metastasis
How Is Mesothelioma Metastasis Treated?
Mesothelioma treatments do not differ substantially between patients with and without metastasis. However, doctors may treat patients with slight metastasis differently than those with extensive metastasis.
Depending on the degree of metastasis, patients may qualify for radiation or some forms of surgery. Stage 3 or 4 mesothelioma patients may not be eligible for aggressive surgery. But they commonly qualify for systemic treatments like chemotherapy and immunotherapy.
Some patients with metastasis may benefit from heated local chemotherapy, such as HIPEC or HITHOC. HIPEC stands for hyperthermic intraperitoneal chemotherapy. It may be used to treat peritoneal mesothelioma. HITHOC stands for hyperthermic intrathoracic chemotherapy. It may be used to treat pleural mesothelioma.
Timely treatment may impact prognosis for patients with any stage of metastasis. But they must receive an accurate diagnosis first. Patients should discuss their mesothelioma risk factors, like asbestos exposure, with a doctor. This information can help the doctor order appropriate tests. This may enable a timely and accurate diagnosis.
Mesothelioma patients with metastasis have effective treatment options. Patients with new or worsening symptoms should discuss these with their doctor. Catching metastasis early may allow for more aggressive treatment and a better prognosis.
