Peritoneal Mesothelioma

Peritoneal mesothelioma is one of several types of mesothelioma that develops in the lining of the abdominal cavity (known as the peritoneum). Caused by asbestos, peritoneal mesothelioma accounts for about 15 – 20 percent of all mesothelioma cases diagnosed throughout the world, with approximately 500 cases in the U.S. diagnosed each year. It is the second-most common form of mesothelioma cancer, and it is almost always fatal.

Due to its location in the body, peritoneal mesothelioma is sometimes referred to as abdominal mesothelioma.

How Peritoneal Mesothelioma Develops

As with all types of mesothelioma, scientific studies have shown the primary cause of peritoneal mesothelioma to be exposure to asbestos. A very small number of people with a specific genetic predisposition may also develop peritoneal mesothelioma after prolonged exposure to erionite, a naturally occurring mineral similar to asbestos.

The exact method by which asbestos arrives in the abdomen is unclear. For the most part, asbestos fibers tend to lodge in the lining of the lungs, where pleural mesothelioma develops. Researchers have continued to look for the ways in which asbestos can reach the abdominal cavity and get lodged in the lining.

The two most common theories of how asbestos is introduced to the peritoneum are described below:

Lymphatic Transport: Throughout the body, there is a network of connected tissues and organs that carries a fluid called lymph, which contains white blood cells. This lymphatic system is critical for helping to fight viruses, infection, and disease. Some experts believe that asbestos fibers enter initially through the lungs, and then are transported through the lymphatic system to the abdominal cavity, where they can become stuck in the peritoneum.

Ingestion: In addition to inhaling asbestos, some fibers may be swallowed, especially if a person is exposed to a significant amount of the deadly mineral at their job, home, school, or another location they frequent. This can also happen with asbestos fibers that get trapped in mucus that eventually is swallowed. The body cannot digest asbestos, and as the fibers move through the digestive system, they may work themselves into the peritoneal cavity and, eventually, into the lining of the abdomen.

Regardless of how the fibers reach the peritoneum, their presence will eventually cause inflammation and, ultimately, tumors. As the tumors grow, they begin to cover the abdominal cavity and eventually may spread (metastasize) to other areas of the body.

What are the symptoms of peritoneal mesothelioma?

Like all forms of asbestos-related cancer, peritoneal mesothelioma can lay dormant for up to fifty years. The disease is usually difficult to diagnose, especially if the patient has not experienced exposure to asbestos for many years. Once symptoms do start to appear, however, it is critically important to have them checked, since early detection is the single most important factor in determining prognosis.

Unfortunately, early diagnosis is not always possible, and it is never easy. The symptoms of peritoneal mesothelioma can be easily confused with those of other, more common diseases. Therefore, many victims go undiagnosed or are improperly diagnosed for months before the proper conclusion is determined.

Symptoms of peritoneal mesothelioma include:

• Abdominal pain (acute to severe)
• Swelling of the abdominal region due to fluid accumulation
• Breathing difficulties
• Loss of appetite and/or weight loss
• Bowel obstruction
• Nausea
• Vomiting
• Weakness
• Fever
• Anemia

Symptoms may vary with each patient and may depend on a number of factors, including:

• Tumor location and size
• Patient’s age
• General health of the individual

When presenting symptoms for diagnosis, it’s important for patients to tell their doctor about any exposure to asbestos, even if the exposure occurred many years ago. This knowledge will help your doctor come to an appropriate diagnosis, and it may spare you a number of unnecessary tests and a long wait before beginning treatment.

Diagnosing peritoneal mesothelioma requires a biopsy

Diagnosis of this rarer form of mesothelioma is much the same as with pleural mesothelioma. Your doctor likely will order one or more imaging tests, including a traditional X-ray, an MRI, a CT scan, or a PET scan. Each of these tests have their pros and cons; however, none of them can be used to positively diagnose peritoneal mesothelioma on their own, or even used in combination. At best they can only show where malignant tumors may be formed.

Once an imaging test is performed, doctors who suspect mesothelioma as a possible diagnosis will typically order additional tests – usually to rule out other diseases. Of these additional tests, a tissue biopsy is the only one that can be used to make a conclusive diagnosis. The biopsy is performed using a peritoneoscopy or laparotomy to take a sample of the tissue around the abdominal cavity. The biopsy can be uncomfortable, but it is usually over in just a few minutes.

Once the biopsy is taken, the sample tissue will be scrutinized under a microscope. This process, known as histological analysis, is how the pathologist determines whether the tumor cells are cancerous. If the tumor turns out to be mesothelioma, the pathologist will further categorize it according to its cell type: epithelioid, sarcomatoid, or biphasic (a combination of the other two).

Treatment typically takes multiple approaches

Once a diagnosis is determined, an oncologist will help determine a course of treatment. In most cases, treating peritoneal mesothelioma will require a multimodal approach – that is, a combination of different techniques. If the disease is diagnosed at a late stage, then some of these treatments may be palliative (designed to relieve pain) rather than curative.

Surgery

Surgery is most often successful in the early stages of mesothelioma, before the disease has had time to spread (metastasized) throughout the body. If surgery is determined to be as a viable option, it will likely involve a procedure known as peritonectomy, in which a portion of the lining and tissue from the abdominal area are cut away to remove the tumor. In such cases, the goal is to remove the entire tumor. If the tumor is unusually large, a lung or a section of the diaphragm may need to be removed as well.

Unfortunately, because peritoneal mesothelioma is often diagnosed in its very late stages, tumor removal by surgery is often not an option.

Radiation

Radiation itself does not cure mesothelioma. However, it can be used to help make other treatments, more effective or to relieve symptoms from the disease.

In attempts to cure mesothelioma, radiation is often used as an additional form of therapy to help kill any cancer cells that may have been left behind after surgery or chemotherapy. This can be done through traditional radiation treatment, which uses an external radiation source to bombard the general abdominal area with radiation. Alternatively, it can be delivered using an internal radiation source through a technique known as brachytherapy.

With late-stage peritoneal mesothelioma, radiation can be used as a palliative measure to relieve pain or reduce symptoms.

Chemotherapy

Chemotherapy is the most common treatment for peritoneal mesothelioma. The most common form of treatment usually uses a combination (often called a “cocktail”) of chemotherapy drugs like cisplatin and pemetrexed to chemically kill fast-growing cells, including cancer cells. Different chemotherapy drugs will be used depending on the individual diagnosis and cell type of the disease.

A relatively new way of treating peritoneal mesothelioma is by delivering chemotherapy drugs to the abdominal cavity. Known as hyperthermic intraperitoneal chemotherapy (HIPEC), this method has been found to be especially effective when combined with cytoreductive surgery (CRS).

Like radiation, chemotherapy can be a palliative measure, relieving uncomfortable symptoms and improving the quality of life for mesothelioma patients.

Emerging Treatments

Clinical trials are offered by researchers through many cancer clinics and health centers for those diagnosed with mesothelioma. These trials usually offer the opportunity to try experimental medications or emerging treatments that have not yet been shown to be completely effective and have not received approval from the FDA and other governmental organizations that oversee health care.

Some of the trials are studying methods such as:

• Immunotherapy – Targeting the immune system to start or enhance the body’s natural immune responses to mesothelioma.
• Gene Therapy – Fixing genetic problems that lead to the development of cancer through the introduction of new, properly working genes into the body.
• p53 Restorative Drugs – New drugs that focus on activating a specific protein that kills or repairs cells with mutated DNA.
• Epigenetic Therapy – Using drugs to fix a person’s epigenome and restore its anticancer capabilities.

Although riskier than traditional treatments, new treatments may offer hope to those whose cancer does not go into remission using standard therapy techniques.

Prognosis for peritoneal mesothelioma is poor

Because it takes so long to diagnose peritoneal mesothelioma, the outcome is usually not positive. As with other forms of the cancer, most victims live for less than a year after diagnosis. The longest-known survivor of mesothelioma lived 19 years after diagnosis, but such cases are extremely rare.

Mesothelioma patient prognosis depends on a variety of considerations:

• The individual’s gender and age
• The stage of the disease at diagnosis
• Mesothelioma cell type
• Exact location of tumors in the peritoneum

Doctors and research scientists continue to look for ways to treat and cure mesothelioma and its symptoms, as well as prolong the lives of those who are affected.