Peritoneal cancer affects the peritoneal cavity, a part of the abdomen. Some types of peritoneal cancers affect females, whereas others are common in males. There are some risk factors for this cancer, such as genetic mutations and hormone replacement therapy.

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This article is about peritoneal cancer and will describe and compare this cancer to ovarian cancer. It will then provide further information about this condition, including the risk factors, symptoms, treatment, and prognosis of peritoneal cancers.

A note about sex and gender

Sex and gender exist on spectrums. This article will use the terms “male,” “female,” or both to refer to sex assigned at birth. Click here to learn more.

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Scientists define peritoneal cancer as cancer that affects the peritoneal cavity.

The boundaries of the peritoneal cavity include the:

  • anterior abdominal muscles
  • vertebrae — bones of the spine
  • pelvic floor — a group of muscles and ligaments that support the:
    • bladder
    • uterus
    • bowel
  • diaphragm — the thin muscle below the lungs and heart that separates the chest from the abdomen

What the cavity contains?

The peritoneal cavity contains the:

  • omentum — a fold of the peritoneum, the thin tissue that lines the abdomen, surrounding the stomach and other abdominal organs
  • ligaments — connect bones to other bones
  • mesentery — composed of two thin layers of tissue, which surround and contain the vascular (blood) and lymphatic (lymph nodes) structures supplying either the small intestine or colon

In peritoneal cancer, cancer cells grow within the serous membrane, a component of the peritoneal cavity.

There are two main types of peritoneal cancer: primary and secondary.

Primary peritoneal cancer (PPC) is when cancer originates in the peritoneal cavity itself. Secondary peritoneal cancer is when cancer spreads from a different body part to the peritoneal cavity.

PPC is rare. Data collected in the Czech Republic for a 2021 study suggests that this peritoneal cancer may affect around 4.36 per 1 million people. Secondary peritoneal cancer is more common, affecting around 99.0 per 1 million people.

Vs. ovarian cancer

Ovarian cancer affects the ovaries and is a common cause of cancer-related death. While ovarian cancer is different from peritoneal cancer, there are some important connections between the two.

Research shows that certain forms of peritoneal cancer have symptoms indistinguishable from some forms of ovarian cancer. However, PPC typically only affects the ovaries minimally

Read more about the specific symptoms.

Ovarian cancer can also cause secondary peritoneal cancer. Indeed, in 75% of ovarian cancer diagnoses, doctors will also find secondary peritoneal cancer. This is because peritoneal cells provide an environment for cancer cells to multiply easily.

There are several risk factors for peritoneal cancer, and the National Cancer Institute lists the following:

Who else is affected?

The research suggests that some forms of peritoneal cancer, such as extraovarian primary peritoneal carcinoma (EOPPC), affect only females. Other forms of peritoneal cancer, such as malignant peritoneal mesothelioma (MPM), can affect older males.

Researchers remain uncertain about all of the possible causes of peritoneal cancer. However, scientific work has uncovered some possible causes or contributing factors.

Many things can cause primary peritoneal cancers. EOPPC may arise due to genetic mutations. Scientists found a BRCA1 gene mutation in around 17.6% of people with EOPPC. Meanwhile, asbestos exposure may cause MPM 33–50% of the time.

A secondary peritoneal cancer has the same cause as whichever cancer it came from. For example, if someone develops peritoneal cancer from ovarian cancer, both cancers will have the same cause. Several genetic mutations, such as those in the KRAS and BRAF genes, are common causes of ovarian cancer.

As a 2022 review explains, peritoneal cancer symptoms are nonspecific as these symptoms are also similar to other conditions, such as ovarian cancer. Common symptoms of peritoneal cancer include:

Anyone experiencing symptoms of peritoneal cancer should seek a doctor’s advice.

As the review also explains, staging for peritoneal cancer works differently in primary and secondary cases.

Doctors only have two stages for primary peritoneal cancers — stages 3 and 4. At stage 3, the tumor solely exists within the peritoneal cavity. At stage 4, cancer has metastasized to other body parts.

These stages also have sub-divisions:

  • Stage 3A: Cancer exists within the pelvic organs and the abdomen’s lymph nodes.
  • Stage 3B: Cancer exists within the peritoneum outside the pelvis and within the lymph nodes outside the peritoneum. The tumor is 2 centimeters (cm) or less.
  • Stage 3C: This is similar to stage 3B, except the tumor is more than 2 cm.
  • Stage 4A: There is a buildup of fluid around the lungs.
  • Stage 4B: Cancer has spread to body parts beyond the peritoneal cavity, such as the lungs, liver, or groin lymph nodes.

By contrast, secondary peritoneal cancers have five stages:

  • Stage 0: Any existing cancer is microscopic.
  • Stage 1: A tumor exists in one part of the abdomen. It is less than 5 millimeters (mm).
  • Stage 2: The tumor is still less than 5 mm. However, it begins to affect the whole abdomen.
  • Stage 3: Several tumors exist, and they are larger than 5 mm but smaller than 2 cm.
  • Stage 4: Several larger tumors exist, and they are larger than 2 cm.

Outlook based on stage

The survival rate for primary peritoneal cancers is around 11–17 months. The survival rate for secondary peritoneal cancer is even shorter.

Secondary peritoneal cancers of stages 0–2 have a survival rate of 5–10 months. Later stages have a survival rate of 2–3.9 months.

Scientists continue to improve cancer treatment options, and the outlook varies based on cancer stage and treatments available.

To diagnose cancer, doctors biopsy tissue samples or perform a paracentesis — a body fluid sampling procedure.

Scientists also have many different ways to diagnose peritoneal cancer. These include:

  • Imaging techniques: Technologies such as CT, PET, and MRI scans can help doctors find tumors within the peritoneum.
  • Paracentesis: The removal of fluid samples from the abdomen. Doctors can test those samples for cancer cells.
  • Laparoscopy: This involves using keyhole surgery to remove tiny samples of suspected tumors. Doctors can then test these samples in the laboratory.

In some cases, doctors may need to use several diagnostic techniques for one person.

Treatment options for peritoneal cancer will vary from person to person. However, studies show that combined approaches tend to be the most effective.

A combined approach will include surgery to remove tumors and treatments including chemotherapy and postoperative drug and radiation therapies. Finally, this approach may also use specific drugs to target specific cancer-causing genes.

Peritoneal cancer affects the peritoneal cavity. It can arise for many reasons, most of which are unknown but can include a combination of medical, genetic, or lifestyle factors. Doctors will use various imaging methods and invasive procedures to diagnose this type of cancer.

Scientists continue to improve treatment options for people with peritoneal cancer to improve their general outlook.