Metastases to Peritoneum

When cancer from organs like the stomach, colon, or ovaries spreads to the membrane lining your abdomen, it creates a serious condition that requires specialized care, but new treatments are helping patients live longer and better lives.

Table of contents

• What is Metastases to Peritoneum?
• The Peritoneum and Your Abdomen
• Who is at Risk?
• Signs and Symptoms
• Complications
• How is the Condition Diagnosed?
• Treatment Options

What is Metastases to Peritoneum?

Peritoneal metastases, Peritoneal carcinomatosis, Peritoneal cancer

Metastasis occurs when cancer spreads from its original site to other parts of the body. Peritoneal metastases refer to cancer that has spread to the peritoneum from other organs^[1]. The peritoneum is a membrane that covers the inner lining of the abdominal cavity and the organs lying in there. It helps to support these organs and contains the blood vessels and nerves that supply them^[1].

When cancer spreads from other organs to the peritoneum, it is considered advanced and denotes Stage IV disease in most cases^[1]. This type of cancer spread is also called late-stage or metastatic cancer^[2].

It is important to understand that metastases to the peritoneum are different from cancers that start in the peritoneum itself. Cancers that develop from the peritoneum itself, such as primary peritoneal cancer or peritoneal mesothelioma, are very rare^[1].

The Peritoneum and Your Abdomen

• Peritoneum
• Abdominal cavity
• Pelvic cavity

Your peritoneum is a membrane that lines your abdominal and pelvic cavities. It coats several organs housed inside these cavities^[2]. The space in the abdominal cavity covered by the peritoneum is known as the peritoneal cavity^[1].

Who is at Risk?

Any type of cancer can spread to your peritoneum, but certain cancers are more likely than others to lead to peritoneal metastases^[2].

Patients who suffer from cancers mainly of abdominal origins such as gastric cancer (stomach), ovarian cancer, colorectal cancer, appendix cancer, and pancreas cancer are at risk of developing peritoneal metastases^[1]. The primary cancers most likely to lead to peritoneal metastases are ovarian cancer (most common), colon cancer, stomach cancer, pancreatic cancer, appendix cancer, and rectal cancer^[2].

Less commonly, other cancers can also spread to the peritoneum. In about 10% of people with peritoneal metastases, cancer starts in organs outside of the abdominal cavity. When this happens, cancer cells use the bloodstream or lymphatic system to reach your peritoneum^[2].

People who think they may be at risk should discuss this with their doctor^[1].

Signs and Symptoms

Peritoneal metastases don’t usually cause symptoms until they affect a large portion of your peritoneum^[2]. Some people may notice symptoms early, while others may not feel anything until the disease has gotten worse. Symptoms often become more noticeable when cancer cells grow and start affecting nearby organs, such as the intestines, bladder, and stomach^[4].

The most common symptoms include^[4]:

• Abdominal swelling or bloating: This is the most common symptom. Swelling is caused by fluid buildup, called ascites, in the belly. Someone may feel that they are gaining weight in the belly despite exercise. Women in menopause may appear as if they are pregnant.
• Abdominal pain or discomfort: This is often described as vague cramping or pressure-like pain.
• Loss of appetite: Someone may feel full quickly, even after small meals.
• Losing weight without trying: This weight loss is not related to changes in diet or activity.
• Fatigue: Someone may feel very tired, even after resting.
• Nausea and vomiting: These are often linked to bowel issues caused by tumor pressure.
• Bowel changes: These can include constipation.

Other symptoms may include a swollen abdomen, abdominal mass, low back pain, and unexplained weight loss or weight gain^[2].

These symptoms are common across lots of conditions. And many of them aren’t as serious as peritoneal metastases. But only a healthcare provider can rule out cancer in your peritoneum^[2].

Complications

Complications related to peritoneal metastases can significantly affect a patient’s quality of life^[1][6]:

• Ascites: Peritoneal metastases tend to produce fluid in the abdomen, known as ascites, which causes abdominal distension. This fluid buildup can make the abdomen feel tight and uncomfortable.
• Intestinal obstruction: Peritoneal metastases may cause blockage of the intestines, preventing normal digestion and bowel movements.
• Hydronephrosis: The kidney ureters may be blocked by peritoneal metastases. This may affect the kidney function and could lead to kidney damage if not treated.

How is the Condition Diagnosed?

The diagnosis of peritoneal metastases can be difficult^[6]. Peritoneal metastases often spread across the abdominal lining without forming distinct masses. Because of this, doctors usually need to combine imaging, fluid tests, and sometimes surgery to confirm a diagnosis^[8].

Tests that diagnose peritoneal metastases include^[2][8]:

• Imaging tests: Procedures may include a CT scan, MRI, PET scan, or a combination of these. They show how much the cancer has spread throughout your peritoneum. These scans help identify visible tumor spread, fluid buildup, or organ involvement. However, imaging is often not sensitive enough to detect smaller cancers or early peritoneal disease. Therefore, a negative scan does not rule out peritoneal metastases.
• Blood tests: Your provider may need to check your blood for tumor markers (substances that tumors release). High levels of certain proteins may be a sign of peritoneal metastases.
• Paracentesis: Your provider may remove a sample of the fluid in your abdomen if you have ascites. They can test the sample in a lab for signs of the primary cancer (the cancer that’s spread).
• Biopsy: Your provider may remove a sample of the tumor and test it in a lab for cancer cells.
• Peritoneal washing cytology: In this test, fluid from the abdominal cavity is surgically collected during a minor procedure. It’s then examined under a microscope. Healthcare professionals use peritoneal washing cytology to check for cancer cells floating in the peritoneal fluid. Even when no visible cancer is present, a positive result is a strong sign that peritoneal spread has happened.
• Staging laparoscopy: This is a safe, minimally invasive surgical procedure used to look directly inside the abdominal cavity using a small camera. It allows healthcare professionals to inspect the peritoneum, find hidden tumors, and take tissue or fluid samples. This test is especially valuable for finding peritoneal metastases that are too small to be seen with imaging.
• Circulating tumor DNA (ctDNA): This is a newer blood test that looks for small pieces of DNA from cancer cells in the blood. It can help find peritoneal cancer that doesn’t show up on scans.

Imaging such as CT or MRI scans, needle drainage of ascitic fluid for analysis, keyhole surgery, or a combination of these may be required to confirm the diagnosis of peritoneal metastases^[6].

The Peritoneal Carcinomatosis Index (PCI) is one resource your healthcare provider may use during the diagnostic process to plan treatment. Using this index, providers map the location of the tumor in your abdomen and your small intestine. They assign a score based on the tumor’s size. This information helps your provider know how likely it is that surgery can get rid of the tumor^[2].

Treatment Options

The standard treatment for peritoneal metastases is cytoreductive surgery (CRS) with hyperthermic intraperitoneal chemotherapy (HIPEC)^[2]. While there’s no cure, surgery and this form of chemotherapy help people with this disease live longer^[2]. Treatments can help slow disease progression and help you live longer^[2].

The goal of cytoreductive surgery is to remove all visible tumors in your peritoneum. During this procedure, surgeons work to take out as much of the cancer as possible from the peritoneal lining and affected organs^[2].

HIPEC destroys any remaining cancer cells after surgery. This treatment involves delivering heated chemotherapy directly into the abdominal cavity during or immediately after cytoreductive surgery. The heat helps the chemotherapy work better and reach cancer cells more effectively^[2].

The combined approach of cytoreductive surgery with HIPEC has helped some people feel better and live longer. Sometimes these treatments may even lead to a cure in selected patients^[4].