What Is Peritoneal (Abdominal Lining) Cancer? Symptoms and Treatment

Peritoneal "abdominal lining" cancer, or primary peritoneal cancer, occurring in only 6 out of 1 million people, is one of the rare cancers. To illustrate how rare it is, ovarian cancer occurs in approximately 120 out of 1 million people. However, estimating the exact number is difficult because a significant proportion of women diagnosed with advanced ovarian cancer (up to 15 percent) are thought actually to have peritoneal cancer. In many respects, peritoneal cancer resembles epithelial (classic) ovarian cancer: it causes similar symptoms, looks similar under the microscope and responds to the same types of treatment.

Because primary peritoneal cancer often causes no symptoms early on, it is generally diagnosed at an advanced stage. It tends to spread early because the peritoneum has an abundant supply of blood and lymphatic vessels.

Note 1: Primary peritoneal cancer means that the cancer originates in the cells of the abdominal lining itself. Cancerous changes in these cells are less common than metastasis (spread) to the peritoneum from other abdominal organs. In this respect, primary peritoneal cancer resembles primary brain tumors; brain metastases are likewise more common than primary brain tumors.

Note 2: This article concerns primary peritoneal carcinomatosis. Another primary cancer of the peritoneum, peritoneal mesothelioma, is discussed in this article in detail.

What Is Peritoneal (Abdominal Lining) Cancer?

The peritoneum is a two-layered membrane covering the digestive system, liver and reproductive organs. It consists of epithelial cells and has an appearance resembling a wrapping around the organs. The small amount of fluid between its two layers protects the organs and allows them to move freely against one another without sticking.

Some other cancers can spread to the peritoneum, but peritoneal cancer begins in the cells forming the peritoneum (called primary peritoneal cancer).

The Relationship Between Primary Peritoneal Cancer and Ovarian Cancer

There are many similarities between primary peritoneal cancer and epithelial ovarian cancer , including their most common symptoms and treatments. The abdominal lining (peritoneum) and the ovarian surface originate from the same tissue during fetal development.

There are views that the peritoneal cells giving rise to peritoneal cancer may be residual ovarian cells left in the abdomen during development. These similarities between the cancers help with treatment planning because epithelial ovarian cancer is much more common and has been researched more extensively.

Although peritoneal and ovarian cancer are similar, there are also important differences . People diagnosed with peritoneal cancer tend to be older than those with ovarian cancer. Regarding treatments (below), debulking surgery (surgery to reduce tumor burden) is more likely to succeed in peritoneal cancer, but overall survival is lower (debulkingmeans reducing a tumor's mass or volume as much as possible). This suggests differences in tumor biology between the two cancers.

What Are the Symptoms of Peritoneal Cancer?

Just as ovarian cancer is known as a silent disease because it lacks symptoms in its early stages, people with peritoneal cancer also experience few symptoms until the disease is quite advanced. Symptoms of abdominal lining cancer:

• abdominal bloating
• diffuse abdominal pain
• frequent urination
• and feeling full when eating are among its vague signs. These symptoms are not specific to this cancer.

Other symptoms:

• bowel changes (usually constipation)
• abnormal vaginal bleeding
• a palpable abdominal mass
• unintentional weight loss

As the disease progresses, fluid called ascites may accumulate in the abdomen, causing abdominal pain, discomfort, nausea and vomiting. It may also cause shortness of breath as abdominal pressure pushes upward against the lungs. Fatigue is also common.

Complications (Problems Caused) by Peritoneal Cancer: These can include bowel obstruction (sometimes requiring a stoma, or an opening between the bowel and the outside of the body) and urinary tract obstruction caused by tumors blocking the ureters, sometimes requiring a stent or nephrostomy tube (a tube from the kidney to the outside of the body).

What Are the Causes and Risk Factors for Peritoneal Cancer?

Although the exact cause of peritoneal cancer is unknown, cancer begins when a series of mutations in peritoneal cells results in uncontrolled growth. Peritoneal cancer is much more common in women and has risk factors similar to those for ovarian cancer.

Most risk factors include:

• being over age 60
• a history of breast cancer
• a history of endometriosis
• obesity

Long-term use of talcum powder below the waist is also thought to be associated with increased risk.

In contrast, some factors are associated with a lower-than-average risk of developing the disease. These include oral contraceptive (birth control pill) use (the reduced risk may persist for up to 30 years after stopping the medication), tubal ligation, giving birth particularly before age 35, and breastfeeding. Some studies have not suggested that taking nonsteroidal anti-inflammatory drugs such as ibuprofen and aspirin could reduce the risk.

As mentioned, some people undergo preventive surgery to remove their fallopian tubes and ovaries (hysterectomy and salpingo-oophorectomy) because of a family history of ovarian cancer or a BRCA gene mutation. Although this preventive approach can reduce epithelial ovarian cancer risk by up to 90 percent, the risk of peritoneal cancer remains.

The Genetic Basis of Peritoneal Cancer

A family history of ovarian, fallopian tube or peritoneal cancer increases a person's risk of peritoneal cancer, and approximately 10 percent of these cancers are considered hereditary . Lynch syndrome (hereditary nonpolyposis colon cancer) and certain other genetic syndromes, or having a BRCA gene mutation, increase the risk. Women carrying a BRCA gene mutation have a roughly 5 percent increased risk of peritoneal cancer even if their ovaries have been removed.

• Related topic: Familial, Hereditary and Sporadic: Concepts Often Confused in Cancer

How Is Peritoneal Cancer Diagnosed?

Even in people at high risk of developing primary peritoneal cancer, there is no effective screening test for early diagnosis.

After listening to symptoms and performing a physical examination, doctors may order several tests when considering the diagnosis.

Blood Tests

The blood test CA-125measures a tumor markerthat may be elevated in people with peritoneal cancer. However, CA-125 levels can rise in many conditions, from pelvic infections to pregnancy, and levels may be normal even when cancer is present. Another test, called OVA1, is used before surgery to predict whether ovarian or peritoneal cancer is present. It uses a combination of 5 biomarkers to estimate the probability.

Imaging Tests

Oncological radiological examinationscan help evaluate symptoms of peritoneal cancer. Ultrasound (transvaginal ultrasound) is often the first test performed. An abdominal and pelvic (groin area) magnetic resonance (MR) or computed tomography (CT) scan can also be useful. After a person is diagnosed, PET-CT is very useful for evaluating treatment response.

Biopsy and Laparoscopy

Often, a biopsy is needed to confirm or rule out a diagnosis. During laparoscopy, several small incisions are made in the abdominal skin, and instruments are inserted to take a biopsy from the abdominal lining and remove tissue samples from the abdomen or pelvis.

Laparoscopy can also provide important information about treatment. A 2018 study found that laparoscopy was highly sensitive in determining who might respond well to optimal cytoreductive surgery. Because cytoreductive surgery, meaning "removing all visible tumors as completely as possible," is so important, laparoscopy can be very helpful in deciding which patients should undergo this operation and when the risks might outweigh the benefits.

When ascites is present, a procedure called paracentesis may be performed to drain some of the fluid and help breathing (described in detail below). This fluid can also be examined under a microscope for cancer cells.

Other Diagnoses That Can Be Confused With Peritoneal Cancer

Several conditions can mimic primary peritoneal cancer. These include different types of ovarian cancer, abdominal abscesses, cystic collections of fluid, bile or lymphatic fluid, and other cancers that have metastasized to the peritoneum.

What Are the Stages of Peritoneal Cancer?

Unlike many cancers divided into stages 1-4 (I-IV), primary peritoneal cancer has no early stage. Regardless of symptoms and signs, this cancer is always stage 3 or stage 4 at diagnosis. In stage 3 disease, cancer may have spread outside the pelvis or to lymph nodes near the back of the abdomen (retroperitoneal lymph nodes). In stage 4 peritoneal cancer, the tumor has generally spread (metastasized) to abdominal organs such as the liver or to other parts of the body such as the lungs.

How Is Peritoneal Cancer Treated?

Treatment for peritoneal cancer depends on several factors, including the cancer's location, stage and the person's overall health. Treatment options include:

Surgery

For people undergoing surgery, it is recommended that a specialist known as a gynecologic oncologist perform the procedure. Studies have shown better outcomes when these specialists operate than when a general surgeon or gynecologist does so. Finding a gynecologic oncologist experienced in treating women with ovarian and peritoneal cancer is also important.

The most frequently performed operation is an oncological surgeryknown as cytoreductive or debulking surgery. The aim is to remove an optimal amount of cancer, but removing all of it is usually impossible.

In this operation, the surgeon removes the uterus (hysterectomy), both fallopian tubes and ovaries (bilateral salpingo-oophorectomy), and the main site of cancer in the peritoneum. Sometimes the omentum, the fatty tissue layer surrounding the intestines, is also removed (omentectomy). Depending on the cancer's location and extent, nearby lymph nodes and the appendix may also be removed (the peritoneum itself cannot be removed). Peritoneal cancer can spread widely within the abdomen, and often most tumor areas are removed.

Cytoreductive surgery may seem confusing to people familiar with other cancers. For example, if lung or breast cancer cannot be completely removed surgically, operating does not improve survival (although it may reduce pain and complications). In contrast, in peritoneal and ovarian cancer, removing as much tumor as possible is known to contribute to survival. Chemotherapy works better after the amount of tumor present has been reduced. The goal of cytoreductive surgery is generally "optimal" tumor removal rather than complete cancer removal. After optimal cytoreductive surgery, no cancer area larger than 1 centimeter (approximately half an inch) should remain in the abdomen. Chemotherapy may be given during or after surgery.

The Peritoneal Cancer Index and Its Importance

The peritoneal cancer index (peritoneal cancer index, PCI) is used to assess the extent of peritoneal cancer throughout the peritoneal cavity. For this purpose, the cavity is divided into 13 well-defined regions (see the figure below). In each of the 13 regions, the largest tumor nodule is measured. If no tumor is visualized, that region scores "0." If the largest tumor nodule is smaller than 0,5 cm, the score is "1." Tumors measuring between 0,5 cm and 5 cm score "2." Lesions larger than 5 cm score "3." If there is layering or a confluence of multiple small tumor nodules, the score is "3." The peritoneal cancer index is calculated by adding the scores from all 13 regions, with a maximum of 39 (13 × 3) points.

As the peritoneal cancer index decreases, disease-free and overall survival increase. In general, aggressive treatments are not recommended for patients with a high PCI score.

Chemotherapy

In peritoneal cancer, chemotherapy is generally used during or after surgery. It can be given intravenously (into a vein) or injected directly into the abdominal cavity (intraperitoneal chemotherapy). Clinical research suggests that a quite different treatment may benefit peritoneal cancer. In this approach, heated chemotherapy drugs are injected into the abdomen during surgery (intraoperatively) or after surgery; this is called hyperthermic intraperitoneal chemotherapy (HIPEC). In heated intraperitoneal chemotherapy, the drugs are heated to 42 degrees before being injected into the abdomen. Heat makes cancer cells more sensitive to chemotherapy.

Targeted Cancer Drugs

Targeted drugs are medications that target specific intracellular pathways involved in the growth of a cancer cell.

• The drug bevacizumab, which acts on angiogenesis , received approval in 2016 for use with chemotherapy in peritoneal cancer from the FDA .
• Lynparza (olaparib) can be used in women carrying BRCA gene mutations.
• The anti-EGFR drug Tarceva (erlotinib) may be effective in some patients with peritoneal cancer.
• In addition, some primary peritoneal cancers overexpress HER2 (are positive), similarly to some breast cancers, and may respond to HER2-targeted treatments .
• In 2018, Rubraca (rucaparib)received FDA approval for primary peritoneal cancer treatment based on a treatment that resulted in significantly longer progression-free survival than placebo.

Radiotherapy

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

Clinical Trials

New ways to treat peritoneal cancer are currently being evaluated in several clinical trials . These include other targeted treatments and immunotherapy drugs.

Supportive / Palliative Care

Unfortunately, most people are diagnosed with peritoneal cancer only at an advanced stage, when a complete cure is not possible. However, many things can be done to extend survival and improve quality of life .

Paracentesis (inserting a needle through the skin into the abdominal cavity to drain fluid) can reduce shortness of breath. Nutritional consultation (dietitian support) can help with cancer-related loss of appetite and perhaps reduce the risk of cancer cachexia .

Pain control is important because this cancer can be very uncomfortable, and nausea management can also improve quality of life. Complementary and alternative treatments are not effective in shrinking tumors, but some complementary approaches may help people cope with symptoms associated with cancer and its treatments. Integrative therapies such as yoga, meditation, massage, acupuncture and more are offered at most larger cancer centers.

Prognosis (Disease Outlook)

Although the prognosis of peritoneal cancer is generally poor, the cancer can be completely eliminated in a small proportion of patients. Few studies have assessed survival rates, but certain factors are associated with better survival. These include no cancer in the lymph nodes, optimal or complete cytoreductive surgery, and use of hyperthermic intraperitoneal chemotherapy.

Coping With Peritoneal (Abdominal Lining) Cancer

Coping with any cancer is difficult, and in addition to the usual concerns, many people have never heard of peritoneal cancer. This can feel very isolating, especially when you see the support available to people with other cancers (such as breast cancer). Although the relative rarity of the disease makes finding a local peritoneal cancer support group difficult, online peritoneal cancer communities allow people to connect day and night when needed.

Any cancer diagnosis can be frightening, but peritoneal cancer can be particularly challenging because it is rare and is most often diagnosed at an advanced stage. You may feel discouraged as you begin learning about your cancer.

However, it may help to remember that treatment options for advanced cancers have improved substantially in recent years. Even when the chance of completely curing peritoneal cancer is very low, appropriate approaches can substantially control cancer-related signs and symptoms, allowing patients to live comfortable and fulfilling lives.