What is a Malignant Peritoneal Mesothelioma?

Malignant peritoneal mesothelioma is a rare cancer that develops in a body membrane called the peritoneum. This membrane lines the abdominal cavity and abdominal organs, providing protection and support and acting as a structural framework for nerves, blood vessels and lymphatic vessels. Malignant peritoneal mesothelioma is a highly aggressive cancer and is very difficult to diagnose and treat. As such, it progresses rapidly and is almost always fatal.

There are several types of mesothelioma, each originating in a different body location. Pleural mesothelioma arises in the lungs, pericardial mesothelioma in the heart and testicular mesothelioma in the testicles. All types of malignant mesothelioma, including peritoneal mesothelioma, are caused by exposure to asbestos. Malignant peritoneal mesothelioma accounts for between 20 percent and 33 percent of all types of mesothelioma.

One of the reasons this cancer is difficult to treat is because diagnosis is often a lengthy process. Symptoms of malignant peritoneal mesothelioma include abdominal pain, abdominal swelling, appetite loss, weight loss and fluid build-up in the abdomen. These symptoms are highly nonspecific and can develop as a result of many other abdominal diseases. For this reason, reaching an accurate diagnosis can take several months, during which time the cancer can continue to advance. Diagnosis typically involves blood tests and medical imaging tests such as X-rays, a CT scan and an MRI scan.

Metastasis of peritoneal mesothelioma is relatively uncommon and tends to occur late in the progression of the disease. Even so, the cancer can advance significantly without spreading outside the abdominal cavity. It is unusual for peritoneal mesothelioma to advance to the lymph nodes or blood, but it can spread throughout the abdomen and metastasize to bone, the lungs and the liver.

The main difficulty in treating malignant peritoneal mesothelioma is the ease with which the cancer spreads in the abdominal cavity. Surgery can improve patient prognosis significantly, but in many cases, the rapid spread of the disease, combined with late diagnosis, means that surgery is not possible. When surgery is carried out, it generally is followed up with chemotherapy. If surgery is not possible, treatment typically is limited to chemotherapy alone.

Peritoneal mesothelioma often is treated with a type of chemotherapy called intraperitoneal or intracavity chemotherapy. In this type of treatment, chemotherapy drugs are applied to the abdominal cavity via a catheter instead of being administered intravenously. This method reduces the severity of side effects from chemotherapy and improves the efficacy of the treatment by concentrating therapy at the site where it is most needed.

These treatments can alleviate the symptoms and extend the patient's lifespan, but they cannot cure this type of cancer. The average survival time of peritoneal mesothelioma is just six to 12 months after diagnosis. In cases where an early diagnosis is made, a patient has an approximately 50 percent chance of living five years or more.