Peritoneal Mesothelioma

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.

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, and no amount of exposure is considered safe.

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.

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 peritoneoscopy or laparotomy, which is a procedure to take a sample of the tissue from around the abdomen. The biopsy can be uncomfortable, but it is usually over in just a few minutes.

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.

The Four Main Stages and Their Characteristics

Stage 1

• Localized
• No metastasis or lymph node involvement
• Curative treatment options
• Best prognosis

Stage 2

• Localized
• Tumor has metastasized with minimal spread to lymph nodes
• Curative treatment is an option

Stage 3

• Localized to one side of the body
• Tumor has spread to nearby organs and lymph nodes
• Treatment options are usually palliative and non-surgical

Stage 4

• 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 the PCI scores can also be translated to the staging system used for pleural mesothelioma.

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. The average life expectancy of peritoneal mesothelioma patients is one year. Thanks to advancements in treatment, patients have started to see an improved life expectancy compared to the other forms of mesothelioma, with even as many as half the patients surviving five years or more.

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. 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.

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.

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 patients, a minimally-invasive surgery called paracentesis may also be an option for more palliative benefits. The operation removes the fluid build up in the peritoneum, called ascites, to relieve symptoms like breathing issues 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.