Peritoneal Cancer

Primary peritoneal cancer (PPC) forms in the peritoneum, the thin tissue that lines the abdominal wall and covers the organs inside the abdomen. In primary peritoneal cancer, the cancer begins in the peritoneum itself and has not spread there from another part of the body.

The cells in primary peritoneal cancer look very much like the most common type of ovarian cancer cells. This is because the lining of the abdomen and the surface of the ovary come from the same kind of tissue. For this reason, primary peritoneal cancer is staged and treated in much the same way as ovarian cancer. (See Ovarian Cancer.)

Types & Stages

Primary peritoneal cancer is usually an epithelial cancer, which means it begins in the surface layer of cells that lines the abdomen. The most common form is high-grade serous carcinoma. This type often grows and spreads quickly, and it shares many features with high-grade serous ovarian and fallopian tube cancers.

Because these cancers are so similar, primary peritoneal cancer uses the same staging system as ovarian and fallopian tube cancer:

• Stage I means the cancer is limited to the ovaries or fallopian tubes. True primary peritoneal cancer is not usually diagnosed at this stage, since it begins in the lining of the abdomen and pelvis.
   
• Stage II means the cancer has spread to nearby pelvic organs or tissues, or it is primary peritoneal cancer found mainly in the pelvis.
   
• Stage III means the cancer has spread to the lining of the abdomen beyond the pelvis or to nearby lymph nodes.
   
• Stage IV means the cancer has spread to distant parts of the body, such as the inside of the liver or spleen, the lungs or the fluid around the lungs.

Your care team will use the cancer type, stage, tumor grade and your overall health to recommend a treatment plan.

Signs & Symptoms

Primary peritoneal cancer often causes no symptoms early on. When symptoms do appear, they can be mild or similar to other common conditions, which can make this cancer hard to find early.

Visit a doctor if you are experiencing any of these symptoms:

• Bloating
• Abdominal or pelvic pain or pressure
• Feeling full quickly when eating
• Trouble eating or loss of appetite
• Urinary urgency or needing to urinate more often
• Constipation or other changes in bowel habits
• Swelling in the abdomen
• Unexplained fatigue

Many of these symptoms can be caused by conditions that are not cancer. Still, it is important to pay attention to your body. If these symptoms are new, last more than a few weeks or are unusual for you, talk with a healthcare provider.

Diagnosis

Tests and procedures used to diagnose primary peritoneal cancer may include:

• Physical exam and medical history. Your doctor asks about your symptoms, personal health history and family history, and performs a physical exam to check your overall health.
   
• Pelvic exam. During a pelvic exam, your doctor feels the pelvic organs to check for anything unusual and looks for signs of fluid in the abdomen, called ascites.
   
• Blood tests. Blood tests may check your overall health and look for tumor markers. A CA-125 test measures a protein that can be higher in people with peritoneal or ovarian cancer. Your doctor may also measure a protein called HE4, which can be raised by some peritoneal cancer cells. These tests cannot confirm cancer on their own, but they can offer helpful clues.
   
• Imaging tests. Imaging tests, such as ultrasound, CT, MRI or PET scans, may be used to look for tumors and to learn whether the cancer has spread. Primary peritoneal cancer can be hard to see on these tests, so normal images do not always rule it out.
   
• Laparoscopy. This procedure uses a thin, lighted tube with a small camera inserted through a few very small incisions in the abdomen. It lets the doctor view the inside of the abdomen and collect tissue samples.
   
• Biopsy. During a biopsy, a small sample of tissue is removed and examined under a microscope by a pathologist. This is the only way to confirm whether cancer is present and what type it is.

Treatment

Treatment for primary peritoneal cancer depends on the stage of cancer, whether it has spread, tumor features, your overall health and your personal goals. Because it behaves like ovarian cancer, it is treated in a similar way.

Treatment may include:

• Surgery followed by platinum-based chemotherapy. This is the standard approach for primary peritoneal cancer. Surgery is used to remove as much cancer as safely possible, and chemotherapy that includes a platinum-based medicine is given to treat any remaining cancer cells.
   
• Cytoreductive surgery, also called debulking surgery. This surgery aims to remove all visible cancer, or as much as can safely be removed. Removing as much tumor as possible can help chemotherapy work better and may improve outcomes.
   
• Hyperthermic intraperitoneal chemotherapy (HIPEC). In select cases, heated chemotherapy may be delivered directly into the abdominal cavity during surgery, where it can reach cancer cells on the surfaces of organs. HIPEC is used by experienced surgical teams and is not right for everyone.
   
• Chemotherapy. Chemotherapy uses medicines to kill cancer cells or slow their growth. It may be given before surgery to shrink tumors, after surgery to treat remaining cancer cells or for cancer that returns.
   
• Targeted therapy. Targeted therapy uses medicines that focus on specific features of cancer cells. Tumor testing can help show whether targeted therapy may be an option.
   
• PARP inhibitors. These targeted medicines may help certain cancers, especially those with BRCA gene changes or other features that affect DNA repair. They are often used as maintenance therapy after chemotherapy in select cases.
   
• Bevacizumab. This targeted medicine works by limiting the blood supply that tumors need to grow. It may be added to chemotherapy or used as maintenance therapy in some advanced or recurrent cases.
   
• Immunotherapy. Immunotherapy helps the immune system recognize and attack cancer cells. It may be an option for some advanced or recurrent cancers with certain tumor features.

Clinical trials may also be available. These research studies test new treatments or new ways to use current treatments. Ask your care team whether a clinical trial may be right for you.

Causes & Risk Factors

The exact cause of primary peritoneal cancer is not always known. It begins when cells in the peritoneum develop changes in their DNA that cause them to grow out of control. Because it is closely related to ovarian cancer, it shares many of the same risk factors.

Factors that may increase the risk include:

• Older age. The risk increases as you get older, and it is more common after menopause.
   
• Family history. Having a close blood relative with ovarian, fallopian tube, primary peritoneal or breast cancer may increase risk.
   
• Inherited gene changes. Changes in the BRCA1 and BRCA2 genes can raise the risk of primary peritoneal cancer, even in people who have had their ovaries removed.
   
• Lynch syndrome. This inherited condition, also called hereditary nonpolyposis colorectal cancer, can increase the risk of several cancers, including those in the abdomen and pelvis.
   
• Endometriosis. Endometriosis, a condition in which tissue similar to the lining of the uterus grows outside the uterus, may increase the risk of certain related cancers.
   
• Hormone therapy after menopause. Some forms of hormone therapy used after menopause may increase risk, especially when used for a long time.
   
• Obesity. Having obesity may increase the risk of developing this cancer and can affect overall health.

Having one or more risk factors does not mean you will develop primary peritoneal cancer, and some people with the disease have no known risk factors. Talk with your healthcare provider about your personal risk.

Screening

There is no recommended routine screening test for primary peritoneal cancer for people at average risk who do not have symptoms.

Tests such as CA-125 blood tests and transvaginal ultrasound have not been shown to reliably find this cancer early in people without symptoms, and they can lead to extra testing without lowering the risk of dying from the disease.

People at higher risk, such as those with BRCA gene changes, Lynch syndrome or a strong family history of ovarian, breast or related cancers, should talk with a healthcare provider or genetic counselor. In some high-risk situations, doctors may discuss closer monitoring, genetic testing or risk-reducing options.

If you have symptoms that are new, persistent or unusual for you, do not wait for a screening test. Talk with a healthcare provider about your symptoms and whether further evaluation is needed.

This information is for general education only and is not a substitute for medical advice. Please consult a qualified healthcare provider for diagnosis, treatment recommendations and guidance based on your personal health history.