Peritoneal cancer: 8 questions, answered

Peritoneal cancer is a rare cancer that develops in the peritoneum, the tissue made of epithelial cells that line the abdominal wall. It’s sometimes called primary peritoneal cancer. It may also start in other areas, like the fallopian tube or ovaries.

Peritoneal cancer has characteristics similar to both ovarian cancer and fallopian tube cancer, and it is treated in the same way.

Here are answers to some common questions I hear about peritoneal cancer.

Is peritoneal cancer the same as ovarian cancer?

Peritoneal cancer is not the same as ovarian cancer, but the two types of cancer share similar characteristics. The cells look the same under the microscope. Peritoneal cancer spreads and behaves the same way as ovarian cancer. We also treat it the same way.

What causes peritoneal cancer?

We’re not sure what causes peritoneal cancer. We do know that the biggest risk factor for developing it is having a hereditary predisposition, such as a BRCA1 or BRCA2 genetic mutation.

What are the symptoms of peritoneal cancer?

Peritoneal cancer symptoms are often non-specific. This means they can also be symptoms of many other conditions. Symptoms may include:

• Unexplained weight gain or weight loss
• Abdominal fluid buildup (called ascites)
• Feeling full after eating only a small amount of food
• Change in bowel habits
• Abdominal pain

More symptoms can develop if the disease has spread. For example, if fluid builds up in one of your lungs, you may have shortness of breath. If the disease spreads to your bowel, it may lead to a bowel obstruction, which can cause nausea, vomiting and constipation.

How is peritoneal cancer diagnosed?

There is no routine screening for primary peritoneal cancer. When you visit your doctor with symptoms of peritoneal cancer, your doctor will go over your medical history and give you a physical exam. You may have lab work and a CT scan to look for masses in the ovary or other places. Some patients may have a laparoscopy. During this procedure, tissue is removed and biopsied. This can confirm a peritoneal cancer diagnosis.  

Much like ovarian cancer, peritoneal cancer is often diagnosed at an advanced stage. This is because symptoms are often mistaken for other, less serious conditions. About 80% of patients with peritoneal cancer will be diagnosed when the disease has already advanced to stage III or stage IV disease.

Anyone diagnosed with primary peritoneal cancer should get genetic testing. If the test shows that you have a genetic mutation, your family members may be more likely to develop the disease. It can also affect your treatment options.

How is peritoneal cancer treated?

We treat peritoneal cancer the same way as ovarian cancer and fallopian tube cancer. Patients typically undergo both surgery and chemotherapy. The sequence depends on the patient’s health as well as the tumor’s stage, size and location. 

Patients may have surgery first to remove as much of the tumor as possible followed by chemotherapy. Some patients will start with chemotherapy and then have interval cytoreductive surgery followed by three more cycles of chemotherapy.

Even if we think we have removed all the disease during surgery, we know there is often minimal residual disease, microscopic cancer cells that we cannot see in scans or tests. So, chemotherapy is almost always part of the treatment plan to treat those remaining cells, especially when the cancer is in advanced stages.

How does peritoneal cancer spread?

Peritoneal cancer can spread all over the abdomen. I describe it to patients like a powdered donut. A powdered donut has small bits of powder all over it. With peritoneal cancer, there are tiny little nodules that exfoliate throughout the abdomen and pelvis. Sometimes, it can spread to the liver and bowel, but in other cases, the disease is just on the surface of these organs.

Does peritoneal cancer have a high rate of recurrence?

Recurrence is common in patients with peritoneal cancer. About 80% of patients will have cancer that responds to treatment. But up to 80% of those patients will have the cancer come back at some point. Only about 10% of patients are cured after primary treatment.  

What research is being done to advance the treatment of peritoneal cancer?

As a medical community, we’ve been trying to figure out how to lower the chances of recurrence. Maintenance therapy has become an option for some patients. Genetic testing can show certain biomarkers that help us choose the best maintenance strategy. If the genetic testing is negative, we send the tumor for testing to help us pick better maintenance strategies for patients.

MD Anderson has clinical trials focusing on minimal residual disease. There’s also research being done on the different kinds of relapse. Patients with peritoneal cancer usually get the chemotherapy drug carboplatin as their first medication. Carboplatin is a platinum-based agent. If the cancer comes back less than six months from the last time the patient received a platinum-based agent, we consider the cancer to be platinum-resistant. If the cancer comes back more than six months after the patient last received a platinum-based agent, the cancer is considered platinum-sensitive. Patients with cancer that is platinum-resistant often don’t do as well, but there have been some recent advances.

In March, the Food and Drug Administration (FDA) approved the antibody drug conjugate mirvetuximab soravtansine-gynx for the treatment of some patients with platinum-resistant primary peritoneal cancer.  This happened because research showed patients who received this drug had a higher overall survival rate and progression-free survival rate compared to those who received chemotherapy.   

We’re all putting our heads together to develop new strategies to better treat people with peritoneal cancer. I’m hopeful we’ll get more answers in the future.

Roni Nitecki Wilke, M.D., is a gynecologic oncologist at MD Anderson.

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