Approximately 15 – 20 percent of all mesothelioma cases are peritoneal.
Asbestos likely reaches the abdomen through ingestion or via the lymphatic system.
The average life expectancy of a peritoneal mesothelioma patient is 1 year.
Surgery with a heated chemotherapy wash (HIPEC) is the most effective treatment.
Peritoneal mesothelioma, sometimes called abdominal mesothelioma or diffuse malignant peritoneal mesothelioma is a form of mesothelioma that develops in the lining of the abdominal cavity (known as the peritoneum). It 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.
The peritoneal form is the second-most common form of the disease, and while almost always fatal, it has a more favorable prognosis than other types of mesothelioma. New treatments, particularly cytoreductive surgery and HIPEC, a heated chemotherapy wash, have extended survival times, with many patients living with the disease for seven years or more.
- Cause // Asbestos inhalation or ingestion
- Location // Abdominal lining (peritoneum)
- Common Symptoms // Abdominal pain
- Treatment // Surgery
- Prognosis // 6 – 12 months
What Causes Peritoneal Mesothelioma?
As with all types of mesothelioma, the peritoneal form is caused by exposure to asbestos. A very small number of people with a specific genetic predisposition may also develop malignant peritoneal mesothelioma after prolonged exposure to erionite, a naturally occurring mineral similar to asbestos.
It’s unclear exactly how asbestos gets into the abdomen, but the two most common theories are lymphatic transport and ingestion.
How Asbestos Reaches the Abdomen
The lymphatic system is a network of connected tissues and organs critical for helping fight viruses, infection, and disease. Some experts believe 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.
Asbestos fibers may be swallowed, either directly or after being trapped in mucus during inhalation. 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.
Asbestos fibers in the peritoneum can cause inflammation that ultimately leads to cancer. As the tumors grow, they will spread throughout the abdomen and eventually to other parts of the body.
Diagnosing the Symptoms of Peritoneal Mesothelioma
Regardless of the type, mesothelioma can take anywhere from 10 to 50 years to begin to show symptoms. Even when the cancer first starts to present, peritoneal mesothelioma symptoms can easily be confused for other illnesses or diseases because they are nonspecific.
Symptoms of Peritoneal Mesothelioma
- Breathing difficulties
- Abdominal swelling due to fluid accumulation
- Loss of appetite
- Weight loss
- Bowel obstruction
- Abdominal pain (acute to severe)
Patients experiencing any of these symptoms should be sure to inform their doctor of any potential past exposure to asbestos, even if it occurred many years ago. Malignant mesothelioma and other asbestos-related diseases develop slowly over the course of decades.
All forms of mesothelioma are also notoriously difficult to diagnose, leaving some patients with misdiagnoses for months, which ultimately delays treatment. Peritoneal mesothelioma is most commonly mistaken for other abdominal cancers, irritable bowel syndrome (IBS) or ovarian cancer. There are also two types of extremely rare forms of peritoneal mesothelioma that can also hinder proper diagnosis.
Rare Forms of Peritoneal Mesothelioma
- Also known as well-differentiated papillary mesothelioma (WDPM)
- Most often develops in the peritoneum, but occasionally forms in other parts of the body
- Not definitively linked to asbestos exposure
- Often benign and can be surgically removed
- Favorable prognosis, with some documentation of patients surviving 6 years or more
- Develops in the omentum, a layer of the abdominal membrane that covers organs like the intestines and stomach
- May be a result of peritoneal mesothelioma metastasis
- No standard treatment, but case reports document chemotherapy as an option
- Prognosis is very poor
A diagnosis will typically begin with a variety of tests to rule out other illnesses and types of cancer, including imaging scans, blood tests and biopsies. Currently, a biopsy or tissue sample is the only definitive method to diagnose mesothelioma. The doctor will perform a laparoscopy or laparotomy, to take a sample of the tissue from around the abdomen.
Once the biopsy is taken, a pathologist will scrutinize the sample tissue under a microscope to determine if the cells are cancerous. The doctor will be able to further categorize the cell type and the severity of the abdominal mesothelioma’s progression.
Peritoneal Mesothelioma Staging
Unlike pleural mesothelioma, there is no set staging system for peritoneal mesothelioma because of its rarity. However, doctors may still be able to identify how advanced the disease is and its progression for an individual case. In general, mesothelioma can be staged according to the following characteristics.
- No metastasis or lymph node involvement
- Curative treatment options
- Best prognosis
- Tumor has metastasized with minimal spread to lymph nodes
- Curative treatment is an option
- Localized to one side of the body
- Tumor has spread to nearby organs and lymph nodes
- Treatment options are usually palliative and non-surgical
- Spread to both sides of the body
- Tumor has spread to multiple organs, lymph nodes, and blood vessels
- Treatment is generally palliative
Peritoneal cancers also have another system that helps identify the severity of tumor progression and helps determine what treatments a patient is eligible for. The Peritoneal Cancer Index, or PCI, is a notable tool that has been used by oncologists for several decades. The PCI works by segmenting the abdominal region into 13 distinct sections. Oncologists will then “score” the region based on the size of the tumors present, known as a lesion score, through imaging scans or laparoscopy.
The overall PCI is then calculated by adding the scores for each region together, with the highest PCI being 39. The regional scores and overall PCI will help oncologists determine if the abdominal cancer is localized or has spread. In general, a higher score means larger, more numerous tumors, indicating a more advanced stage and worse prognosis. Some researchers have proposed that the PCI scores can also be translated to the staging system used for pleural mesothelioma.
Peritoneal Cancer Index
- 0: No tumors
- 1: Up to 0.5 cm
- 2: Up to 5 cm
- 3: Larger than 5 cm or multiple tumors
- 1-10 : Stage 1
- 11-20: Stage 2
- 21-30: Stage 3
- 31-40: Stage 4
Patients with a higher PCI may also be considered ineligible for certain treatments, like surgical removal of the tumors or heated intraperitoneal chemotherapy (HIPEC), which are considered the most effective treatments for peritoneal mesothelioma.
Peritoneal Mesothelioma Prognosis
Mesothelioma in all its forms typically has a rather poor prognosis, which can vary based on a variety of factors including the location and stage. Thanks to advancements in treatment, patients have started to see an improved life expectancy compared to the other forms of mesothelioma, with median survival ranging from 3 to 5 years if surgical treatment can be delivered.
Peritoneal Mesothelioma Survival Rate
- Stage 1: Five-year survival of 87%
- Stage 2: Five-year survival of 53%
- Stage 3: Five-year survival of 29%
The cell type can also have a large impact on the prognosis, as it can help show how aggressive the cancerous cells are and may affect the treatment options available. Epithelioid cells account for 50 – 70% of mesothelioma cases. This cell type is most commonly associated with pleural mesothelioma but has also been found in peritoneal patients. It’s the most studied cell type and has the best prognosis, though it can be difficult to distinguish from other diseases like adenocarcinoma.
Sarcomatoid is the rarest cell type, accounting for only 10% of cases, and is most commonly found in peritoneal mesothelioma. Sarcomatoid mesothelioma is also difficult to diagnose and has a higher likelihood of spreading than the other types. The last cell type, biphasic, is a combination of sarcomatoid and epithelial cells. The prognosis for this type will largely depend on the distribution of cells, as the presence of more sarcomatoid cells than epithelial can mean a worse survival rate.
Peritoneal Mesothelioma Prognosis Based on Cell Type
- Epithelioid mesothelioma: 54 months
- Sarcomatoid mesothelioma: 4.6 months
- Biphasic mesothelioma: Not enough data
Treatments for Peritoneal Mesothelioma
Mesothelioma specialists often rely on three standard treatments for any type of mesothelioma: surgery, chemotherapy and radiation. Most often, these treatments are used in tandem, known as multimodal treatment, to have the best effect on a patient’s prognosis. Emerging treatments, like immunotherapy, have also been heavily studied in more recent years to determine their effectiveness for mesothelioma. These types of therapies are currently only available in clinical trials, which can sometimes be limited because of mesothelioma’s rarity but have shown promise in being able to effectively treat the disease and extend overall survival.
Peritoneal Mesothelioma Specialists
Surgical oncologist at University of Maryland Marlene and Stewart Greenebaum Cancer Center
Gastrointestinal surgical oncologist at Washington Cancer Institute
Surgical oncologist at the UPMC Hillman Cancer Center
For peritoneal mesothelioma patients, there are two types of curative treatment, most often used in combination, that have shown the most positive effects in improving life expectancy. For some peritoneal mesothelioma patients, draining the abdominal fluid with a procedure called paracentesis may also be an option to help relieve the pressure in the abdomen. The operation removes the fluid build up in the peritoneum, called ascites, to treat symptoms such as shortness of breath and discomfort and improve overall quality of life.
Cytoreductive Surgery and HIPEC
Many studies have shown the positive effects of treating abdominal mesothelioma with cytoreductive surgery in combination with a heated chemotherapy wash called Hyperthermic Intraperitoneal Chemotherapy (HIPEC). The surgery aims to remove all visible tumors in the abdominal cavity, with the HIPEC being applied throughout the abdomen after to kill any remaining cancer cells.
Some studies have found this combination therapy to give patients a median survival of about 53 months or more, with one study even reporting an overall median survival of 92 months with this treatment. Across these studies, about 40 – 50% of patients have achieved at least five years of survival, while overall only 9% of mesothelioma patients typically survive that long.