Peritoneal Mesothelioma
Peritoneal mesothelioma is a cancer of the peritoneum, which is the lining of the abdomen. It is the second most common type of mesothelioma and with pleural mesothelioma makes up the vast majority of all mesothelioma diagnoses. Incidence rates for peritoneal mesothelioma vary, but it’s thought to occur in ten to twenty percent of malignant mesothelioma diagnoses. There is some evidence to suggest that diagnoses of peritoneal mesothelioma in the United States are on the rise.
While all forms of mesothelioma affect men more than women, if a woman is diagnosed with mesothelioma, it is more likely to be peritoneal mesothelioma than it is pleural mesothelioma. Neither of these types of mesothelioma have effective cures, and the prognosis is often grim: the average survival time varies from 4 – 18 months after diagnosis.
Function of the Peritoneum
The peritoneum is a serous membrane that lines the body’s abdominal cavity and secretes a fluid to provide for increased movement and reduced friction among the organs in the midsection. Like the pleura, there are two parts to the peritoneum: the visceral peritoneum and the parietal peritoneum. The visceral peritoneum covers the internal organs and makes up most of the outer layer of the intestinal tract. The parietal peritoneum lines the abdominal cavity.
Development of Peritoneal Mesothelioma
As with all forms of mesothelioma, peritoneal mesothelioma has been conclusively shown to be caused only by exposure to asbestos. The carcinogenic process, i.e., the manner in which tissue becomes cancerous, is still not fully understood, but it begins with an initial exposure to asbestos. Asbestos fibers are very durable and cannot be fully eliminated by the body’s immune system. Over time, they cause chronic inflammation and the development of a fibrosis that leaves the affected tissue with calcifications and plagues that impede the peritoneum’s proper functioning. In some cases, these antigenic fibers lead to the development of mesothelioma.
Unlike pleural mesothelioma, where it’s clear that fibers were breathed-in and then settled in the pleural cavity and lungs, it is still not understood by scientists just how asbestos fibers become lodged in the peritoneum. There are three theories:
- Asbestos fibers that have been broken down into smaller pieces in the lungs are carried through the blood stream to the abdomen lining.
- Asbestos fibers were ingested with food or drink. Clouds of asbestos dust were common in factories and ships. Some fibers could have settled on workers’ food.
- Inhaled asbestos fibers are transported through the lymphatic system to the peritoneal cavity.
As the incidence of peritoneal mesothelioma increases, more research is being devoted to its study and scientists are hopeful that more advances in our understanding of the disease are right around the corner.
Symptoms and Diagnosis of Peritoneal Mesothelioma
One of the most common symptoms of peritoneal mesothelioma is abdominal pain, due to tumor invasion of the peritoneum which often comprises both its elasticity and its ability to filter fluids throughout the abdominal cavity. However, like the symptoms of pleural mesothelioma, it is often difficult to diagnose peritoneal mesothelioma in its early stages because its symptoms often mimic the symptoms of other abdominal illnesses.
Some of the symptoms shared by peritoneal mesothelioma and other illnesses include:
- Upper abdominal pain
- Abdominal swelling due to fluid retention or tumor growth
- Cough and shortness of breath
- Fever
- Weight loss
- Fatigue
- Anemia
- Digestive disturbances
Because of these similarities and the relative rarity of mesothelioma in the general population, the disease often grows untreated because the doctor was treating a different ailment. More invasivediagnostic techniques are not often used until the symptoms become more pronounced. Thus, when one is actually diagnosed with peritoneal mesothelioma, one’s cancer is often quite advanced. This could mean that multiple tumors have already invaded the peritoneum, that the cancer has spread to the lymph nodes and/or that the cancer has metastasized to other parts of the body, such as the lungs or the heart.
Treatment and Prognosis of Peritoneal Mesothelioma
As we stated in the introduction to pleural mesothelioma, all general prognostic guidelines and treatment regimens for mesothelioma are based on the pleural form of the disease. Because of this, most of the information we have regarding treatment and prognosis of peritoneal mesothelioma is anecdotal. However, this does not mean that the data should be ignored. Scientists have been gathering more and more information about peritoneal disease and clinical studies are ongoing that specifically study treatment regimens for this variety of mesothelioma.
Like all forms of mesotheliomas, there is no cure for peritoneal mesothelioma. However, peritoneal mesothelioma often presents with a better prognosis and a longer life expectancy than does pleural mesothelioma. Histologically, peritoneal mesothelioma is most often of the epithelial subtype, which is the type most amenable to treatment. The sarcomatous subtype rarely presents in peritoneal mesothelioma, so many treatment regimens seem to have a better response rate with peritoneal mesothelioma. While the pleural disease has an average life expectancy of a year to 16 months from diagnoses, it is not uncommon for victims of peritoneal disease to live two to five years after diagnosis.
A notable example of greater-than-average life expectancy, as well as one of the most famous people diagnosed with mesothelioma, was Harvard University professor Stephen J. Gould, an internationally renowned paleontologist and evolutionary biologist. Dr. Gould was diagnosed with peritoneal mesothelioma in 1982. After an initial period of depression, he became hopeful and was determined to not let the statistics regarding life expectancy beat him. When he finally died in 2002, it was from another form of cancer, totally unrelated to his mesothelioma. Dr. Gould has written about his experience with peritoneal mesothelioma and his determination to not let simple statistics dictate his reaction to his diagnosis in the essay, “The Median Isn’t the Message.” We recommend Dr. Gould’s essay for everyone who has been diagnosed with this disease.
Dr. Gould’s experience certainly may not be standard, but his hopeful approach to his diagnosis cannot be discounted. Peritoneal mesothelioma is a very serious disease and it must be taken seriously as such. However, treatments are improving, as are the prognoses of those diagnosed.
