Many types of cancers (like mesothelioma) spread through either direct invasion or the lymph nodes. With unique exceptions, mesothelioma does not spread to a person’s central nervous system. Instead, this condition grows in the cavities where it originates.
Following metastasis, pleural mesothelioma can end up completely encasing the lung and spreading throughout the chest by involving the heart, esophagus, and opposing lung.
Fatalities Due to Metastatic Mesothelioma
While a small number of people die from mesothelioma directly, many people pass away from complications caused by the disease including pneumonia, heart failure, and organ failure.
When mesothelioma enters its final stage, the tumor has already spread to various other organs and tissues including the heart, the abdominal lining, the esophagus, and the diaphragm. Malignant cells create substantial damage to all impacted parts of a person’s body and impair the normal way in which these organs function. The immune system is also substantially disrupted by mesothelioma and is left unable to fight the disease. Cancer cells are also known to infiltrate the lymphatic system and can end up spreading throughout a person’s body.
When Mesothelioma Metastasize
Cancer cells are considered to spread either distantly, locally, or regionally. Metastases that occur in areas throughout a person’s body happen in approximately
10% to 50% of stage 4 cancer.
In stages 1 to 3, cancer cells spread in both the body cavities where they originate and to lymph nodes, while stage 4 cases involve metastasis to “distant” parts of a person’s body.
The progression of cancer throughout a patient’s body is assessed through diagnostic imagery, which utilizes CT, MRI, or PET scans. Physicians often anticipate the spread of cancer when a person cites symptoms that are not routinely linked to mesothelioma. This will often result in the performance of tests to detect distant mesothelioma.
Where Mesothelioma Metastasis
Mesothelioma spreads throughout the body in various ways. Most often, mesothelioma metastasis to the adrenal glands, kidney, liver, or spleen. Metastasis involves the cancer cells traveling throughout a person’s blood or system of lymph nodes to distant parts of that person’s body. After mesothelioma spreads throughout a person’s body, the condition can end up invading organs and lead to the development of secondary tumors.
Cancer cells reach the blood through the process of angiogenesis which creates new blood vessels in a person’s body. Medical professionals are examining methods to both promote and block angiogenesis to create various anti-angiogenic medications.
Some drugs currently evaluated to combat mesothelioma metastasis include thalidomide, semaxanib, and tetrathiomolybdate. In medical trials, these medications have been shown to both stabilize the disease as well increase a person’s chances of survival.
Metastatic Pleural Mesothelioma
For years, medical professionals viewed pleural mesothelioma as a localized illness with a restricted ability to metastasize throughout a person’s body. A 2012 study of 318 mesothelioma patients found that 55.4% of the patients experienced metastases to distant locations. A study of 172 individuals who passed away from pleural mesothelioma discovered the most common locations where mesothelioma spreads include the adrenal glands, kidney, liver, and opposing lung. The spread of cancer to a person’s brain and central nervous system is rarer and occurs in approximately 3% of cases. In late-stage pleural mesothelioma, the disease metastasizes to distant spots in the body in over 10% of cases. Cancer also sometimes spreads to rarer locations. By the time most individuals receive a diagnosis of mesothelioma, cancer is already in its late stages. If cancer spreads to distant spots in a person’s body, treatment choices are often focused on reducing the severity of symptoms instead of treating the illness.
Metastatic Peritoneal Mesothelioma
In its initial stages, peritoneal mesothelioma does not spread past the peritoneal cavity, which includes the intestines, liver, spleen, and stomach. The most common locations where peritoneal mesothelioma metastasis includes the liver, peritoneal lining, and lymph nodes in the abdomen. Some locations where peritoneal mesothelioma less frequently spreads include the heart, lungs, thyroid, bone, brain, skin, pancreas, and soft tissue. As peritoneal mesothelioma develops, cancerous cells spread to organs located nearby as well as to distant locations. Approximately half of the cases involving peritoneal mesothelioma have located metastases during an autopsy.
Metastatic Pericardial Mesothelioma
The localized spread of pericardial mesothelioma often involves the lung, mediastinum, and pleura. Pericardial mesothelioma metastasis in approximately 25% to 45% of patients to lymph nodes, kidneys, and lungs.
Metastatic Testicular Mesothelioma
As metastatic mesothelioma develops in a person’s body, the condition often spreads from the tunica vaginalis to the lymph nodes. After the condition metastasizes, which rarely happens, the condition spreads to the vertebrae, lungs, and liver.
The Factors that Influence Metastasis
Some of the various factors that influence how mesothelioma metastasis include
- Cell type. The pace at which cancer develops is influenced by the type of cells that make up the tumor. For example, tumors composed of epithelial cells are often less aggressive and spread slower, which means that a person has a longer life expectancy than with other types of cells. Both biphasic and sarcomatoid mesothelioma, however, spread more quickly to other parts of a person’s body, which means minimal treatment options exist and a person with these types of cells faces a shorter life expectancy. The two main types of mesothelioma cells are epithelioid and sarcomatoid. The rate and way that cancer spreads depend on the type of cancer cell that a person has. Epithelioid cells are cube-like. When these cells break from the original tumor and spread throughout the body, they travel through the lymphatic system. The shape of these cells results in the slow spread of mesothelioma. Due to these qualities, the cells often stay closer to the initial cancer location and spread throughout the lymphatic system. The lymphatic system is part of the immune system and carries liquid as well as white blood cells throughout the body. The lymphatic system is filled with various filters or nodes that contain waste products and debris. Sarcomatoid cells, however, are large cells tapered at both ends. The round shape of these cells makes it easier for them to travel throughout the body’s bloodstream. In mesothelioma involving biphasic (or mixed-type) mesothelioma, the tumors are a mixture of epithelioid and sarcomatoid cells.
- How a person responds to treatment. Patients with early-stage mesothelioma who respond well to aggressive treatment often have a lower chance of developing metastatic mesothelioma. Surgery can lower the chance of metastasis through the removal of tumors and cancer cells that might spread. Both chemotherapy and radiation can delay and sometimes even prevent metastasis. Radiation has shown to be particularly effective at combating local recurrence. Sometimes, radiation is also utilized to treat tumors that develop in the chest walls.
- Staging. Medical professionals rely on a system of stages to assess the development of mesothelioma. People who are diagnosed with mesothelioma and still in the early stages have the lowest risk of metastasis and the best outcome. These individuals routinely live two to three years. In stages 1 and 2, cancer only spreads locally. People with later-stage mesothelioma are at the greatest risk of metastasis and sometimes already have distant metastasis. Later stage mesothelioma is more challenging to treat because by this time cancer has often already spread to vital organs. Treatment options for people with late-stage mesothelioma are often restricted to palliative options. Advanced mesothelioma has a life expectancy shorter than one year. In stage 3, the condition has spread further and might spread to the esophagus, the lymph nodes, or the other side of a person’s body. In stage 3, the illness has not yet spread to distant organs. In stage 4, the condition spreads to diverse locations including the bones, other lung, or abdominal lining. Stage one has the least degree of metastasis, while stage four has the highest. The most common type of staging system for pleural mesothelioma is the American Joint Committee on Cancer, which considers the size of the initial tumor as well as whether it has spread to a nearby lymph node and if it has spread to any distant sites.
The Symptoms Associated with Metastatic Mesothelioma
Doctors have a difficult time diagnosing mesothelioma after metastasis. The distant spread of mesothelioma often occurs late in the development of cancer and does not always result in symptoms that are easily noticed. If symptoms of metastatic cancer are noticed, these symptoms often impact the location where the cancer has spread. Some metastatic symptoms are similar to those common symptoms of mesothelioma as well as other cancer. Medical professionals often find metastases by luck following medical imagery. The exact type of metastases that a person faces depends on the type of metastatic mesothelioma a person has. Consider the following symptoms
- Metastatic adrenal cancer. Mesothelioma that spreads to the adrenal glands can result in muscle weakness, weight loss, back pain, and abdominal pain.
- Metastatic brain cancer. Some symptoms associated with mesothelioma that spreads to the brain include poor coordination, headaches, memory loss, seizures, and vision changes.
- Metastatic kidney cancer. Mesothelioma that spreads to the kidneys can result in lumps on a person’s body, high blood pressure, pain in the back or side, and anemia.
- Metastatic liver cancer. Mesothelioma that spreads to the liver can result in bloating, jaundice, abdominal pain, and swelling of the legs.
- Metastatic spleen cancer. Some symptoms associated with mesothelioma that spreads to the spleen include abdominal pain and a ruptured spleen.
Treatment Options for Metastatic Mesothelioma
After mesothelioma has metastasized, treatment focuses on both controlling cancer and its associated symptoms as well as increasing a person’s life expectancy. Medical professionals routinely suggest treatment options that reduce pain, increase a person’s quality of life, and maximize the odds of survival. Some options used to treat mesothelioma include
- Anti-angiogenesis. These medications can either stop or slow down the spread of mesothelioma.
- Chemotherapy. Medical professionals have found that chemotherapy can postpone metastasis, improve a person’s chances of survival, and reduce pulmonary symptoms.
- Clinical trials focused on mesothelioma. Many clinical trials have recently published promising results for people diagnosed with metastatic mesothelioma. Medical professionals are relying on new and emerging technology like gene therapy and immunotherapy to improve patient survival chances.
- Gene therapy. Medical professionals are examining the possibility of altering a person’s genes to both avoid and treat some diseases. The focus of gene therapy is to fix problems created by defective genes, which could reduce the spread of metastatic diseases. Gene therapy is currently available to people with mesothelioma only through clinical trials. The treatment involves the introduction of new cells to combat cancer cells. Many types of gene therapy are currently under examination. Each type of gene therapy focuses on combating certain types of cancer and identifying which gene therapy modality is best situated for that certain type of cancer. Among the many trials underway, several gene therapy studies have found success in lengthening the life expectancy of people with mesothelioma. One example of gene therapy is gene transfer which involves introducing genes to the cancer cells to restrict the growth of tumors or entirely kill cancer cells. The most common type of gene transfer involves “suicide genes”, which turn a non-toxic drug into a cancer-killing drug once located inside a tumor. “Suicide” therapy is given through the use of non-viral (or viral) vectors. Another type of gene therapy is oncolytic virotherapy, which is a type of cancer treatment that utilizes a virus to break down mesothelioma cells while leaving cells that are healthy uninjured. Viruses used for this type of therapy include measles, certain types of hepatitis, certain types of herpes, and various other types of illnesses. When a combination of these therapies is utilized, cancer can sometimes be eliminated.
- Immunotherapy. This type of therapy has become one of the most substantial medical advances in treating metastatic mesothelioma. Medical professionals are focused on the potential advantages of this type of therapy, which utilizes a person’s immune system to fight mesothelioma. Several types of immunotherapy are used to treat mesothelioma. Each type of treatment focuses on cancer cells. One type of immunotherapy treatment is cancer cells which work with the immune system to teach the body to combat cancer cells. These vaccines are often made by either altering a person’s immune cells to better respond to cancer cells or by helping immune cells better determine which cells are cancerous. Mesothelioma vaccines work in combination with a person’s immune system to teach the person’s body how to fight cancer cells. Mesothelioma vaccines are often made by altering immune cells to improve how the body responds to cancer cells or by helping the immune cells better distinguish which cells are cancerous. Another type of immunotherapy treatment are cytokines, which are proteins that help the body improve the immune response to cancer cells. Some cytokines help immune system cells grow more quickly, while others help the body fight cancer cells.
- Multimodal therapy. Mesothelioma experts have recently begun to mix traditional therapies with experimental ones. Medical professionals are examining the advantages of combatting metastatic diseases with new types of therapy like gene therapy in combination with existing treatment options.
- Radiation. This therapy can avoid local recurrence as well as reduce pain associated with metastasis of the chest wall.
- Surgery. Various surgical options exist to treat mesothelioma. Extrapleural pneumonectomy is one type of surgery utilized to treat early-stage pleural mesothelioma. Extrapleural pneumonectomy permits the maximum amount of removal of cancer tissue through the extraction of cancerous lung tissue. Recovery routinely takes between six to eight weeks but is sometimes longer to permit the remaining lung sufficient time to take over all critical functions. Extrapleural pneumonectomy is often performed on people in the early stages of the condition when the cancer is restricted to the chest cavity. This treatment permits the maximum removal of cancerous tissue. Mesothelioma is often not diagnosed until it reaches a later stage, which leaves many people ineligible for this type of surgery. Extrapleural pneumonectomy improves breathing and quality of life. Following recovery, patients often feel more comfortable and can return to daily activities. Unfortunately, some people who receive an extrapleural pneumonectomy find that the condition returns to their abdomen.
- Tumor treating fields. This type of treatment can either delay or even prevent the spread of mesothelioma. This treatment was recently approved by the U.S. Food and Drug Administration and is used in combination with chemotherapy to reduce cancer growth and increase a person’s chances of survival. The treatment utilizes alternating electrical fields to restrict cancer growth. The treatment was created by the Novocure company, which began developing the treatment in the early 2000s. The clinical study that resulted in the FDA’s approval of the TTFields to treat pleural mesothelioma found a survival of 18.2 months for people who received the treatment, while patients who received chemotherapy only lived for approximately 12.1 months. While TTFields does not provide a way to cure mesothelioma, the treatment can greatly improve the length of a person’s survival with few side effects. TTFields are distinct from chemotherapy or radiation. Instead, the treatment “jams up” the field found in tumor cells and prevents them from growing. The treatment involves the introduction of electrical fields delivered through pads that are placed on the skin.
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