Important points

For a long time, peritoneal cancer was thought of as a very rare disease. This perception may still be true for specific subtypes of peritoneal cancer, such as malignant mesothelioma and peritoneal pseudomyxoma (PMP). However, every year, hundreds of thousands of patients around the world are diagnosed with peritoneal cancer originating from a primary tumor located in another part of the body, such as colon cancer, gastric cancer or ovarian cancer.

1: 1 million Rare subtypes

Malignant mesothelioma and peritoneal pseudomyxoma are rare subtypes of peritoneal cancer, which affect approximately one or two people per million each year.

10 - 30%

Common causes of peritoneal cancer Peritoneal colon cancer is much more common: At least 10% of patients with colon cancer will develop peritoneal cancer at some point in their disease. For gastric cancer, this percentage is even higher, with an estimate as high as 30% of patients. Worldwide, hundreds of thousands of patients will develop peritoneal cancer each year as a result of a tumor somewhere else in the body.

6 weeks

Six weeks - six months: life expectancy If left untreated, the average survival time for patients with peritoneal cancer can be as short as six weeks in those with pancreatic cancer or six months for patients with colon cancer. Survival time can be considerably longer the proper treatment is provided.

WHAT IS PERITONEAL CANCER?

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All organs of the abdominal cavity - such as the stomach and intestine - and the abdominal wall are covered by a thin layer of cells. This layer is called "the peritoneal line" or "the peritoneum." Unfortunately, the peritoneum can be invaded by malignant cells. This condition is more commonly referred to as "peritoneal cancer," but it has also been called peritoneal surface malignancy ("PSM"), peritoneal carcinomatosis, peritoneal metastasis, or peritoneal pseudomyxoma ("PMP"). Three different possible origins In peritoneal cancer, there are three different potential origins for malignant cells. First, cancer can originate from the so-called mesothelial cells that make up the peritoneum, which results in a very rare type of cancer called "malignant mesothelioma". The second (and also rare) source of cancer cells is a mucus-producing tumor, which is more frequently located in the appendix. This tumor may rupture when it grows, and the rupture will spread mucus-producing cells to the abdomen. Eventually the abdomen fills with mucus, which leads to a condition known as peritoneal pseudomyxoma (PMP). Finally - and being the most common - peritoneal cancer originates from cancer cells that are spread by a primary tumor at another site in the body. The cells travel to the peritoneum and begin to grow on the peritoneal surface. Almost any primary tumor in the body can cause this disease, but the abdominal organs, such as the colon, stomach and ovaries, are the most common organs of origin. Typically the malignant cells will multiply and form small tumor nodules (between 2 to 5mm) on the peritoneum. However, larger tumors are not rare, and sometimes bulky nodule conglomerates can develop in advanced stages. Peritoneal cancer nodules can occur anywhere in the abdominal cavity, but the most common sites include the right diaphragm, small pelvis, omentum and intestinal surface.

Peritoneal Cancer Incidence

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Peritoneal cancer is difficult to diagnose, especially since it is often not possible to detect it using imaging studies. As a result, the incidence of peritoneal cancer has been underestimated, and has been considered a very rare disease. Even today, the reported incidence rates of peritoneal cancer vary widely, but increased awareness has led to the increase in the reported incidence of peritoneal cancer in the most recent studies. However, the "real" incidence is potentially higher because autopsy studies have found peritoneal metastasis unfailing in many cancer patients. Malignant mesothelioma is a truly rare disease since it is diagnosed in about one to three patients per 1,000,000 people per year. The disease is three times more common in men compared to women, and the risk of developing the disease increases with age. Malignant mesothelioma is mainly diagnosed in people 60 years and older, although younger patients have been described. The number of patients is expected to increase in the coming years due to exposure to asbestos. Peritoneal pseudomyxoma (PMP) is another rare subtype of peritoneal cancer. Studies of the incidence of PMP have been hampered by difficulties in the definition and nomenclature of this disease. Most reports suggest that the incidence of PMP is one to two patients per 1,000,000 people per year, and the incidence of PMP slightly higher in women than in men. In contrast to mesothelioma and PMP, peritoneal cancer that originates from a malignant tumor at a site other than the body is much more common and affects hundreds and thousands of patients each year. This form of peritoneal cancer should be considered a mestastatic disease of the primary tumor. Hence, this form is often referred to as "peritoneal metastasis." Virtually, every primary tumor in the human body can cause peritoneal cancer, but tumors of the gastrointestinal tract and ovaries in women are by far the most common sources. It is thought that at least 10% of patients with colon cancer will develop peritoneal cancer during their illness. Patients with gastric cancer even have a higher incidence of peritoneal cancer, which is thought to be approximately 30% of patients. More detailed information on the incidence of specific subtypes can be found in the “Knowledge Base”.

Symptoms of peritoneal cancer

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In early stages, peritoneal cancer may not cause any symptoms. Frequently, peritoneal cancer is even discovered as a finding during surgery for a primary tumor. Even during the asymptomatic stage, the disease can already be widely disseminated and advanced, which supports its reputation for peritoneal cancer as a "silent killer". When the nodules begin to grow on the intestinal surface, they can cause progressive obstruction of the intestinal tract. This obstruction can result in an uncomfortable discomfort of the abdomen, loss of appetite and weight, nausea and constipation. Additionally, nonspecific symptoms, such as tiredness and pain, may occur. Peritoneal carcinomatosis can also result in the accumulation of large amounts of aqueous fluid in the abdominal cavity. This phenomenon is known as "malignant ascites" and eventually results in a grown abdominal cavity. For peritoneal pseudomyxoma, ascites typically consists of mucus, hence the name "jelly abdomen" is sometimes used to describe this specific subtype. Ascites can cause symptoms similar to those of intestinal obstruction, but ascites can also lead to shortness of breath due to pulmonary oppression. Complete bowel obstruction, resulting in vomiting, abdominal pain and the inability to eat and drink, is often a severe and late symptom of peritoneal cancer and can result in the rapid deterioration of the patient's condition.

Peritoneal Cancer Diagnosis

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Peritoneal cancer is usually very difficult to diagnose, but it can be discovered during the examination or surgical treatment of the primary tumor or when a patient develops symptoms related to peritoneal awareness. There is no specific test that is considered ideal for the diagnosis of peritoneal cancer. Most of the time several of these are required. These approaches usually include the following: PHYSICAL EXAMINATION - Sometimes nodules peritoneal tumors or ascites can be detected during physical examination of the abdomen, but this typically occurs only in advanced cases. DETECTION OF TUMOR MARKERS - These are blood studies that may indicate the presence of a malignant tumor in the body, but these studies are not very specific for most cancers, especially peritoneal cancer. The most commonly used tumor markers are Embryonic Carcino Antigen (ACE) for colon cancer, CA 19-9 for pancreatic cancer and CA-125 for ovarian cancer. ULTRASOUND - This test uses sound waves to create a detailed image of the abdominal cavity on a computer monitor. This study is good for ascites detection, but is usually not sensitive enough to detect peritoneal cancer or the primary tumor. COMPUTERIZED TOMOGRAPHY (CAT) - This detailed radiological examination may reveal the presence of peritoneal cancer or ascites in some cases. Unfortunately, a CT scan is not very good for detecting nodules of peritoneal cancer, especially not in the early stages of the disease. In general, tumor nodules should be at least 1cm, which is larger than the size of typical tumor nodules in peritoneal cancer, to be detected by CT. PET-SCAN - This is a study that combines CT with nuclear radiology (positron emission tomography), and is especially useful for detecting metastases outside the peritoneal cavity. Similar to what happens with CT, peritoneal cancer is typically not visualized by PET. BIOPSY - If peritoneal cancer is suspected, a biopsy can be obtained. In a biopsy, a small piece of tissue is removed from the body for microscopic research. The biopsy can be taken after the patient has received local anesthesia through the skin or during a laparoscopy when the patient is under general anesthesia. A biopsy can confirm the presence of cancer cells in the peritoneal cavity. If the primary tumor is located in the gastrointestinal tract, an endoscopy may be necessary to take a biopsy. LAPAROSCOPY - When peritoneal cancer is suspected, a laparoscopy may be performed. This procedure is especially useful for collecting biopsies of tumor nodules and determining the extent of peritoneal cancer. Usually, the extent of the cancer is determined by calculating the peritoneal carcinomatosis index (PCI). PATHOLOGY - Small parts of the tumor can be removed and examined under a microscope. Cancer can be confirmed and tumor aggressiveness can be predicted based on these observations. Using specific techniques, the origin of the tumor can be determined, which is especially useful in cases where the location of the primary tumor is still unknown. ENDOSCOPY - When the primary tumor is potentially located in the gastrointestinal tract, an endoscope can be inserted through the mouth to investigate the esophagus, stomach and duodenum ("esophagogastroduodenoscopy") or through the anus to investigate the large intestine ("colonoscopy"). The deepest layer of the gastrointestinal tract is visualized with the endoscope. Most gastrointestinal tumors originate from the deepest layer and can be detected by endoscopy. In addition to the visualization of the tumor, biopsies of the tumor can be obtained with the endoscope, which can help confirm the presence of cancer and direct subsequent treatment.

Treatment Options

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Not long ago, treating patients with peritoneal cancer was thought of as a useless maneuver. At that time, these patients typically lived only a few weeks to months after diagnosis depending on the severity of the disease, the patient's condition and the origin of peritoneal metastases. Over the past two decades, this has changed and many hospitals around the world now offer treatment for select patients with peritoneal cancer. The treatment is challenging and requires expert medical professionals in this peritoneal condition. The optimal treatment for an individual depends on many factors, including the age, general condition, origin and severity of the carcinomatosis. Ideally, patients with peritoneal cancer are evaluated by a multidisciplinary team composed of an oncologist, an oncologist, a radiologist and a pathologist with knowledge about this pathology. Even today, treatment may not be completely possible for some patients. For example, treatment may not be possible in very advanced cases in which the patient's condition does not allow him to receive it. Fortunately, some form of treatment is possible in many patients. Generally speaking, there are two strategies to treat these patients: Treatment with palliative intent This treatment focuses on prolonging survival and resolving the symptoms of peritoneal cancer as much as possible, but does not intend to cure the patient. Such treatment may include different aspects ranging from pain relief and ascites removal to treatment with systemic chemotherapy and surgery to resolve intestinal obstruction. Treatment with palliative intent This treatment seeks to cure the patient. This approach is typically a multidisciplinary effort combining systemic chemotherapy, extensive surgery to remove all tumor cells from the peritoneum and intraperitoneal hyperthermic chemotherapy (HIPEC) to destroy microscopic tumor cells. Again, patients with peritoneal cancer should seek help from a multidisciplinary team with specific knowledge about their disease whenever possible to complete their optimal treatment.