An Overview of Peritoneal Cancer

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Peritoneal cancer, also called primary peritoneal cancer, is a rare type of cancer, occurring in only around six out of 1 million people.

The exact number, however, is difficult to estimate, as it is thought that up to 15% of people who are diagnosed with advanced serous ovarian cancer could actually have primary peritoneal cancer.

Due to a lack of early symptoms, primary peritoneal cancer is often diagnosed in the advanced stages of the disease; it also tends to spread rapidly due to the abundance of blood vessels and lymphatic vessels in the abdomen and pelvis.

The Peritoneum

The peritoneum is a two-layered membrane composed of epithelial cells that lines the organs of the abdominal and pelvic cavity, covering the digestive tract, liver, and reproductive organs.

The peritoneal membranes and the fluid between the membranes protect the organs, allowing them to move freely against each other without sticking or rubbing.

Some other forms of cancer can spread to the peritoneum, but peritoneal cancer begins within the cells that make up the peritoneum (the reason it is called primary peritoneal cancer).

Peritoneal cancer may develop anywhere within the abdominal or pelvic cavity, and when it spreads, it often spreads to the surface of abdominal and pelvic organs.

Primary Peritoneal Cancer vs. Ovarian Cancer

There are many similarities between primary peritoneal cancer and epithelial ovarian cancer, including similar symptoms, similar microscopic appearance, and their response to similar treatment methods.

The similarity between these two types of cancer is helpful in planning treatment, as more research has been done on epithelial ovarian cancer because it's much more common. Epithelial ovarian cancer occurs in roughly 120 out of 1 million people.

While peritoneal cancer and ovarian cancer are similar, there are important differences as well. For example, people who are diagnosed with peritoneal cancer tend to be older than those with ovarian cancer.

The peritoneum and the surface of the ovary stem from the same tissue in fetal development. There is some thought that the peritoneal cells that give rise to peritoneal cancer may actually be leftover ovarian cells that remained in the abdomen during development.

The chance that debulking surgery will be successful is greater in peritoneal cancer than in ovarian cancer, but the overall survival rate is worse for peritoneal cancer.

Symptoms

People with peritoneal cancer often have few symptoms until the disease is fairly advanced.

When symptoms occur, they are often vague and nonspecific—and include fatigue, abdominal swelling, diffuse abdominal pain, urinary frequency, and a sense of fullness when eating.

Other symptoms may include constipation, bowel changes, abnormal vaginal bleeding, an abdominal mass, or unintentional weight loss.

As the disease progresses, complications can include:

  • Ascites (fluid build-up in the abdomen), causing abdominal discomfort, nausea and vomiting, and shortness of breath due to the pressure of the abdomen pushing upwards on the lungs
  • Bowel obstructions, sometimes necessitating placement of a stoma, hole between the intestine and the outside of the body
  • Urinary tract obstruction due to blockage of the ureters by tumors, sometimes requiring a stent or nephrostomy tube (a tube from the kidney to the outside of the body)

Causes and Risk Factors

It's not known exactly what causes peritoneal cancer, though the process begins when a series of mutations in peritoneal cells results in out-of-control growth.

Peritoneal cancer is much more common in females than in males and has risk factors similar to the risk factors for ovarian cancer.

Risk factors include:

  • Age, with most people who are diagnosed being over the age of 60
  • Having a history of breast cancer
  • The use of hormone replacement therapy (both combination and estrogen-only types)
  • A history of endometriosis, and obesity

The use of talc below the waist is also linked with an increased risk.

In contrast, there are factors that are associated with a decreased risk of developing the disease. These include the use of oral contraceptives (the reduced risk may last 30 years after they are discontinued), having a tubal ligation, giving birth, especially before the age of 35, and breastfeeding.

A few studies suggest that the use of aspirin and nonsteroidal anti-inflammatory drugs such as Advil (ibuprofen) may reduce risk.

Some people have preventive surgery to remove their fallopian tubes and ovaries (hysterectomy and salpingo-oophorectomy) due to a family history of ovarian cancer or a BRCA gene mutation. While this can reduce the risk of epithelial ovarian cancer by up to 90%, the risk of peritoneal cancer remains.

Genetics

A family history of ovarian, fallopian tube, or peritoneal cancer increases the risk of peroneal cancer, and around 10% of these cancers are considered to be hereditary. Having certain genetic syndromes such as Lynch syndrome (hereditary non-polyposis colon cancer) or having a BRCA gene mutation increases the risk.

Women who carry a BRCA gene mutation have roughly a 5% risk of developing peritoneal cancer, even if their ovaries have been removed preventively.

Diagnosis

There is not currently a screening test that has been found effective in the early detection of primary peritoneal cancer, even for those who have an elevated risk of developing the disease.

After listening to symptoms and performing a physical exam, there are a number of tests doctors may order when considering the diagnosis.

Blood Tests

The blood test CA-125 is a tumor marker that may be elevated in people with peritoneal cancer. That said, levels of CA-125 may be elevated in many different conditions, from pelvic infections to pregnancy, and levels may be normal even in the presence of cancer.

Another test, called the OVA1 test, is used to predict the likelihood of ovarian or peritoneal cancer, using a combination of five biomarkers to estimate a probability.

Imaging Tests

Imaging studies can be helpful in evaluating the symptoms of peritoneal cancer. An ultrasound (transvaginal ultrasound) is often the first test performed. A computerized tomography (CT) scan or magnetic resonance imaging (MRI) scan of the abdomen and pelvis may also be helpful.

In addition, an upper and or lower GI series may be ordered.

Biopsy and Laparoscopy

Most often, a biopsy is needed for a definitive diagnosis. When ascites is present, a paracentesis may be done. This is done with the insertion of a needle through the skin into the abdominal cavity to drain fluid. This fluid can be examined under a microscope to look for the presence of cancer cells.

A laparoscopy may also help guide treatment. A 2018 study found that laparoscopy was very sensitive in determining who would likely have a good response to more extensive surgery.


A biopsy is often taken during a laparoscopy, a minimally invasive procedure in which several small incisions are made in the abdomen, and instruments are inserted to remove tissue samples from the abdomen or pelvis.

Differential Diagnosis

There are a number of conditions that can mimic primary peritoneal cancer. Some of these include the different types of ovarian cancer, abdominal abscesses, cystic collection of fluid, bile, or lymph fluid, as well as metastases to the peritoneum from other types of cancer.

Staging

Unlike many cancers that are classified into stages from 1 to 4, primary peritoneal cancer does not have an early stage.

This disease is always defined as stage 3 or stage 4 at diagnosis.

  • In stage 3 disease, cancer may have metastasized (spread) to the peritoneum outside of the pelvis or to lymph nodes near the back of the abdomen (retroperitoneal lymph nodes), but not to other organs outside the pelvis.
  • With stage 4 peritoneal cancer, the tumor has usually metastasized to organs in the abdomen, such as the liver, or to other regions of the body, such as the lungs.

Treatment

The treatment for peritoneal cancer will depend on a number of factors, including the location of cancer, the stage of cancer, and a person's general health.

Surgery

The surgery most often performed is cytoreduction or debulking surgery. The goal is to remove an optimal amount of cancer, but it's often impossible to remove all of the cancer. The peritoneum itself cannot be removed.

After optimal cytoreductive surgery, there are not any areas of cancer left in the abdomen that are larger than 1 centimeter (about half an inch) in diameter.

By reducing the amount of tumor present, survival improves and chemotherapy can be more effective, as it works better if there are only small tumors in the abdomen.

Since optimal cytoreduction surgery is a major procedure, a preliminary laparoscopy may be helpful in deciding if the risks outweigh the benefits.

During cytoreduction surgery, the surgeon removes the uterus (hysterectomy), both fallopian tubes and ovaries (bilateral salpingo-oophorectomy), and the primary location of cancer in the peritoneum. Sometimes the omentum, the fatty layer of tissue surrounding the intestines, is also removed (omentectomy).

Depending on the size and extent of cancer, nearby lymph nodes, as well as the appendix may be removed. Peritoneal cancer can spread extensively through the abdomen, and many areas of the tumor may need to be removed.

Chemotherapy

Chemotherapy is commonly used for treating peritoneal cancer. it can be started during or after surgery, or used alone for tumors that are widespread. Chemotherapy can be given intravenously or injected directly into the abdominal cavity (intraperitoneal chemotherapy).

Hyperthermic intraperitoneal chemotherapy is a fairly unique treatment that has proven beneficial for peritoneal cancer. During this procedure, chemotherapy drugs are heated to 107.6 degrees F. prior to being injected into the abdomen. Heat can kill cancer cells and may make chemotherapy more effective. It is most often used shortly after cytoreductive surgery has been completed with advanced peritoneal cancer.

Immunotherapy may be used in some cases.

Targeted Therapies

Targeted drugs are medications that target specific pathways involved in the growth of a specific type of cancer cell. Avastin (bevacizumab) is approved for use along with chemotherapy (followed by Avastin alone).

Lynparza (olaparib) may be used for women who carry BRCA gene mutations. Olaparib, Rucaparib, and Nirapirib are PARP inhibitors that are approved for treating this type of cancer.

Radiation

Radiation is used infrequently for peritoneal cancer but may sometimes be useful for treating isolated areas of cancer.

Supportive/Palliative Care

Most people are diagnosed with peritoneal cancer only after it is in the advanced stages, when a cure is not possible. Yet, there are many things that can be done to improve quality of life.

  • Paracentesis may improve breathing by draining fluid.
  • Nutritional consultation may help with the loss of appetite associated with cancer, and reduce the risk of cancer cachexia.
  • Management of nausea can improve quality of life.
  • Pain control is important, as this cancer can be very uncomfortable.

Alternative treatments have not been found to be effective for treating cancer, but may help people cope with the symptoms related to cancer and cancer treatments. Integrative therapies such as yoga, meditation, massage, acupuncture, and more, are offered at many cancer centers.

Prognosis

While the prognosis of peritoneal cancer is generally poor, there have been documented cases of complete remission from the disease.

There are few studies looking at survival rates, and factors associated with better survival rates include the absence of cancer in the lymph nodes and complete cytoreduction surgery.

Coping

Coping with cancer is challenging, and the fact that many people have never heard of peritoneal cancer can add to the stress and anxiety of having this diagnosis. This can feel very isolating, especially when you see the support offered to people with other types of cancer.

While you are unlikely to find a support group for peritoneal cancer in your community due to the relative rarity of the disease, you can connect with online peritoneal cancer communities.

The Primary Peritoneal Cancer Foundation has an online support forum and there are also several Facebook groups for people living with peritoneal cancer.

In addition to these resources, some of the cancer organizations that represent ovarian cancer, as well as organizations that support people with many forms of cancer, may also be a source of support. Some, like CancerCare, even provide support groups and communities for friends and family members of people living with cancer as well.

A Word From Verywell

The treatment options for advanced cancer are improving significantly. And even if a peritoneal cancer is not curable, the management of symptoms related to cancer has improved exponentially, and many people are able to live comfortable and fulfilling lives while coping with the disease.

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