Origin of peritoneal cancer

Malignant Mesothelioma

In healthy individuals, the peritoneal cavity of the abdomen is covered by a thin layer of mesothelial cells. Unfortunately, cancer may develop in these mesothelial cells. This type of cancer is called “Diffuse Malignant Peritoneal Mesothelioma” and is often referred to as malignant mesothelioma.

Although the number of patients worldwide with malignant mesothelioma is rising, it is still a very rare disease with an estimated incidence of one to two patients per 1.000.000 inhabitants per year. However, the incidence varies around the world and in some regions, higher incidences are reported. This higher incidence may be linked to asbestos exposure in these areas, but patients without asbestos exposure may also develop malignant mesothelioma. Malignant mesothelioma is more often diagnosed in men than in women, and the incidence increases with age.

Unfortunately, most patients with a malignant mesothelioma present with advanced and widespread disease. Complaints associated with this cancer may include ascites, the inability to eat properly, weight loss and abdominal pain. Sometimes, an abdominal tumor can be felt during physical examination.

It may be hard to diagnose malignant mesothelioma. Radiological examination may suggest the presence of this disease, but an operation is often needed to inspect the abdominal cavity and to take tissue samples for microscopic examination.

With microscopic examination, different subtypes of malignant mesothelioma may be distinguished. The three most common subtypes are epithelioid, biphasic and sarcomatoid. The most common subtype is epithelioid, and this subtype has the best prognosis. The biphasic and sarcomatoid subtypes are less common and more aggressive.

Traditionally, malignant mesothelioma was treated with a combination of surgery, systemic chemotherapy and sometimes radiation. The results of this treatment were bad and survival was poor.

Recently, some positive results have been obtained from using a combination of drugs (cisplatin and raltitrexed/pemetrexed), but long-term survival with chemotherapy alone is not expected. Survival is typically sustained for around one year after diagnosis.

Cytoreductive surgery and HIPEC

Various hospitals around the world now offer a combination of surgery and HIPEC for select patients with malignant mesothelioma. For most patients, complete resection of the peritoneal layer is required, including abdominal organs that are affected by the mesothelioma. After resection, the HIPEC procedure is performed.

With this treatment, survival has increased significantly, and expert centers around the world now have median survival rates of over 50 months. However, prognosis after this treatment varies widely. For example, the prognosis is often better for women, patients who received a complete resection of the tumor and patients with the epithelioid subtype.

Unfortunately, not all patients with a malignant mesothelioma qualify for a HIPEC procedure. Some hospitals do not offer HIPEC for the sarcomatoid type because of the bad prognosis for this subtype.

The role of systemic chemotherapy before or after HIPEC is unclear and is currently under investigation.

Rare subtypes of mesothelioma

Besides the aggressive malignant mesothelioma, two other subtypes are recognized with a more favorable behavior being multicystic peritoneal mesothelioma (MPM) and well-differentiated papillary peritoneal mesothelioma (WDPPM). These subtypes are very rare, carry a much better prognosis and are even considered “benign” by some. However, progression of this tumor in the abdomen may cause severe complaints and progression to a malignant type of mesothelioma has been described. Therefore, resection of the tumor is the treatment of choice which may be combined with HIPEC.