Metastasis refers to the process by which cancer cells spread to other parts of the body. Metastatic mesothelioma refers to mesothelioma cancer which has spread from its original location to another area of the body. Cancer cells traditionally break away from the primary tumor, traveling through the lymph or blood to other locations. However, mesothelioma is unlike other cancers in the way it develops.

One reason mesothelioma is so difficult to treat is that it does not develop the same way standard tumors do. In some forms of cancer, metastasis is predictable, which allows doctors the ability to predict development. However, mesothelioma tumors do not grow as a single, predictable tumor mass which can be surgically removed easily. Instead, mesothelioma cancer tends to spread along nearby surfaces, blood vessels and nerves, making complete removal through surgery or radiation challenging, except in rare situations.

Treatment Considerations  

In addition to mesothelioma’s relative rarity, which means doctors have far fewer opportunities to observe the best treatments, this metastasis characteristic can limit other treatment options for patients as well. Besides its impact on surgery, a tumor’s localization plays a large part in the doctor’s ability to target only cancerous areas with radiation and chemotherapy as well. Unintentionally impacting healthy tissues can further weaken patients and compromise their strength. Although doctors are continually developing new techniques to refine the use of both chemotherapy and radiation therapy, through improved techniques of imaging and delivery, the cancer’s unique metastatic qualities make this difficult.  

Staging

Due to mesothelioma’s latency period and general symptoms early on, this cancer is rarely diagnosed in its early stages. The cancer possesses a typical latency period, which is the delay between asbestos exposure and tumor development, of 20 to 50 years. Furthermore, symptoms of mesothelioma are often not extraordinary and easily mistaken for signs of less serious ailments, like the common cold or flu.  The American Cancer Society explains symptoms of pleural mesothelioma include the following:

• Pain in the lower back or side of the chest
• Shortness of breath
• Cough
• Fever
• Sweating
• Fatigue
• Weight loss
• Trouble swallowing
• Hoarseness
• Swelling in the face and arms
• Muscle weakness

Symptoms of peritoneal mesothelioma, which is the next most common form, can include the following:

• Abdominal pain
• Swelling or fluid buildup in the abdomen
• Weight loss
• Nausea and vomiting

This means mesothelioma is often diagnosed in its later stages, when it may have metastasized to distant locations. Furthermore, some medical professionals believe mesothelioma travels faster than many other forms of cancer due to its location near the lung and in reach of an oxygen source. This oxygen supply may provide the support it needs to develop quickly, or even spread throughout the bloodstream.

The TNM system of staging further explains that mesothelioma can be divided into resectable versus unresectable cancer. In general, cancers in stages I, II, or III have the potential to be resected, though there are exceptions. However, because of this cancer’s rarity, hidden symptoms and latency period, it is often diagnosed in its fourth stage, meaning it has metastasized to the point where it is no longer resectable.  

At this point, chemotherapy or radiation therapy may be used, though treatments generally take on a palliative nature, lessening the discomfort of symptoms and improving the patient’s quality of life. Although survival rate statistics based on the TNM stage of the cancer are hard to determine, it is a general rule that survival rates are better for patients with cases of mesothelioma which can be surgically operated on than patients with cancer which has metastasized greatly.

References:

American Cancer Society

National Cancer Institute