Peritoneal cancer is a rare type of cancer that occurs within the pelvic or abdominal cavity. It is closely related to epithelial ovarian cancer, the most common type of ovarian cancer, which affects the ovaries, and fallopian tube cancer. Since 2014, the International Federation of Gynecology and Obstetrics has grouped peritoneal cancer with these two cancers because of their similarities. All three types of cancer arise in the same type of tissue and behave similarly. Additionally, the methods to diagnose and treat all three conditions are identical.
Peritoneal cancer affects the thin tissue lining that covers the organs within the abdominal cavity and pelvic region, known as the peritoneum. This type of cancer almost exclusively affects women, who are diagnosed most frequently at age 65 or older.
Peritoneal cancer, like ovarian cancer, is often diagnosed at a late stage. Patients and doctors often miss the cancer at earlier stages because its symptoms are vague, and no routine screening tests look for this condition.
Treatments are available for peritoneal cancer, but their effectiveness varies, depending on how early doctors begin treatment and individual patient factors.
What is peritoneal cancer?
Peritoneal cancer affects the thin membrane within the abdominal or pelvic region. This thin lining, the peritoneum, helps to support the abdominal organs, keeping them in place.
There are two types of peritoneal cancer:
- Primary peritoneal cancer, which originates in the fallopian tubes, peritoneum, or outer lining of the ovaries and affects the peritoneum within the abdominal/pelvic region.
- Secondary peritoneal cancer, which occurs when a patient’s cancer from another area of the body has advanced and then spreads (or metastasizes) to the peritoneum.
What causes peritoneal cancer?
Doctors aren’t sure what causes peritoneal, fallopian tube, or epithelial ovarian cancer, but it can occur when a person has a genetic mutation that causes tumor suppressor genes, such as BRCA1 or BRCA2, to malfunction. Such a mutation encourages ovarian, peritoneal, and fallopian tube cells to multiply uncontrollably, leading to cancer. That being said, most patients with this cancer do not have a family history or genetic mutation.
What are the symptoms of peritoneal cancer?
Women with peritoneal cancer may experience one or more of the following symptoms:
- A distended abdomen (bloating)
- Abdominal or pelvic pain
- Nausea and/or vomiting
- Constipation or other changes in bowel habits
- Increased urinary frequency
- Abdominal mass
- Feeling full sooner than usual
- Unexpected weight loss
What are the risk factors for peritoneal cancer?
Women are at increased risk of peritoneal cancer if they:
- Are 65 or older
- Have a personal or family history of ovarian or fallopian tube cancer
- Have a family history of peritoneal cancer
- Have a personal or family history of Lynch syndrome (and inherited cancer syndrome that predisposes people to certain kinds of cancer
- Have used hormone replacement therapy to relieve menopause symptoms
- Have had endometriosis
- Have obesity
Mutations to certain genes put women at increased risk of peritoneal cancer, including:
- Other genes related to homologous recombination (e.g., Rad51c)
How is peritoneal cancer diagnosed?
Doctors can detect and diagnose peritoneal cancer after learning about a patient’s medical history, performing a physical examination, and using diagnostic tests.
Although symptoms of peritoneal cancer are vague, it is important to let your doctor know how long you have had pelvic pain, bloating, nausea, and/or indigestion. Also mention whether and for how long your appetite and bowel habits have changed, and if you have unintentionally lost weight because you’ve felt full sooner than expected. Tell your doctor if you have a family history of ovarian or fallopian tube cancer, have been diagnosed with endometriosis, or took hormone therapy during menopause. If you feel that your symptoms are being dismissed, consider seeking a second opinion.
During a physical exam, a doctor should perform a pelvic exam.
If a doctor suspects peritoneal cancer, you may receive one or more of the following tests:
- A CA-125 blood test, to look for elevated levels of the CA-125 protein, which may indicate ovarian, fallopian, or peritoneal cancer
- Imaging tests. Doctors may want to see if a tumor or other abnormalities are on the peritoneum, ovaries, or fallopian tubes. To do this, they may order:
- An X-ray of the chest or abdominal cavity
- An abdominal or transvaginal ultrasound, which uses sound waves to create images of the pelvic region
- A computed tomography (CT) scan, which uses X-ray imaging technology to create a series of images of the pelvic region
- A magnetic resonance imaging (MRI) scan, which uses a strong magnet and radio waves to create detailed images of the pelvic region
- A positron emission tomography (PET) scan, to help doctors identify any cancer cells within the body. Before the scan, a patient is injected with a small amount of a radioactive substance, which makes cancer cells stand out on PET scan images
- A biopsy. If doctors locate a tumor during imaging tests, they need to determine if it is cancerous. When doctors suspect peritoneal cancer, depending on the location of the tumor(s), they may choose to start with a biopsy to determine the origin of the tumor or proceed directly to surgery.
How is peritoneal cancer treated?
Peritoneal cancer is treated using one or more of the following options:
- Surgery. Depending on the distribution of the disease and patient factors, surgery may be the first treatment recommended for peritoneal cancer. During surgery, doctors attempt to remove the tumor without rupturing it. They also typically remove the uterus (hysterectomy), with or without one or both ovaries and fallopian tubes, as well as any other tissue that appears to be affected.
Next, doctors will determine the stage of the cancer by performing a biopsy of the tumor, along with a sample of fluid removed from the peritoneal cavity. (If no fluid is present, doctors perform “pelvic washings,” adding saline to the peritoneal cavity, then removing some to test it.) They may also biopsy nearby lymph nodes.
In rare situations, depending on features determined from pathology reports after surgery, some patients may not need additional treatment; however, doctors most often recommend chemotherapy.
- Chemotherapy. Chemotherapy treatment involves IV drugs designed to destroy or damage cancer cells. Women with peritoneal cancer may have chemotherapy drugs placed directly within the peritoneum, which may have a greater effect on the cancer while reducing side effects system-wide. For patients with multiple tumor locations and for whom surgery may not be feasible at the time of diagnosis, they may be treated first with chemotherapy to shrink the tumors followed by surgery.
Patients usually receive more than one chemotherapy medication because the combination of drugs makes the treatment more effective. Doctors use imaging scans to measure the success of these treatments.
Chemotherapy drugs that are used to treat peritoneal cancer include:
- Targeted therapy. Targeted therapy uses specific oral or IV drugs that attack cancer cells without affecting normal, healthy cells. Patients with a recurrence of peritoneal cancer may be treated with targeted therapy treatments plus chemotherapy drugs. Adding targeted therapy treatments into the regimen makes it easier for the body to fight a cancer recurrence. A patient may receive:
- Bevacizumab, a monoclonal antibody that attaches to the cancer cells’ growth factor protein, preventing the cells from growing and spreading
- Poly (ADP-ribose) polymerase inhibitors, a class of drugs designed to prevent cancer cells from repairing their own DNA, which helps to kill them
What is the outlook for people with peritoneal cancer?
When peritoneal cancer is diagnosed and treated early (Stage IA or IB), 90% of patients remain cancer-free five years after treatment. If peritoneal cancer is not discovered until the cancer has spread to other sites in the body, only 15% to 20% of patients live five years or more. Recurrence rates are high for peritoneal, ovarian, and fallopian tube cancer.
Patients should see their doctors several times a year during the first five years after surgery, then annually, to monitor their health.
What makes Yale unique in its treatment of peritoneal cancer?
“Smilow Cancer Center offers patients with peritoneal-based cancers a world-class, personalized treatment approach for these rare and often aggressive cancers,” says Yale Medicine gynecologic oncologist Mitchell Clark, MD. “Not only will patients receive cutting-edge standard of care with expert surgical teams, but they will have access to a range of leading clinical trials for new and promising treatments not available at most centers. At Yale, patients can expect a multidisciplinary team of physicians, nurses, social workers, pathologists, integrative medicine experts, and geneticists who provide all aspects of cancer care from surgery to recovery with an excellent quality of life. We will help patients understand the unique characteristics of their cancer to design a personalized approach to treatment that help women diagnosed with this disease live longer, healthier lives while minimizing treatment related side-effects.”