Malignant Peritoneal Neoplasm

Malignant peritoneal neoplasm is a serious cancer affecting the peritoneum, the thin membrane lining the abdomen and covering internal organs. This rare condition can develop directly in the peritoneum or spread from cancers in nearby organs, and often goes unnoticed until it reaches advanced stages.

Table of contents

• What is Malignant Peritoneal Neoplasm?
• Types of Peritoneal Cancer
• Areas of the Body Affected
• Who is at Risk?
• Signs and Symptoms
• How is it Diagnosed?
• Treatment Options
• What to Expect

What is Malignant Peritoneal Neoplasm?

Malignant peritoneal neoplasm, also called peritoneal cancer, is a serious condition that develops in the peritoneum, which is a thin, delicate sheet of tissue that lines the inside of the abdomen and covers the organs within it^[1]. The peritoneum is made of epithelial cells, which are cells that protect the surfaces of your body. This membrane also produces fluid that helps organs move smoothly inside the abdomen^[1].

When cancer develops in the peritoneum, cells begin to grow abnormally and out of control. This can happen when the peritoneum itself becomes cancerous, or when cancer from another organ spreads to this membrane^[3]. The disease is rare, with providers diagnosing fewer than 7 in 1 million cases each year^[1].

Types of Peritoneal Cancer

Healthcare providers classify peritoneal cancer based on where it first begins. Primary peritoneal cancer starts directly within the cells that make up the peritoneum itself. This type develops when the peritoneal cells themselves become cancerous and begin growing abnormally^[1].

Secondary peritoneal cancer, also called peritoneal carcinomatosis, starts elsewhere in the body and then spreads to the peritoneum. This is the more common form. Cancer cells can travel from organs such as the ovaries, colon, stomach, pancreas, appendix, or rectum to reach the peritoneal membrane^[1][4]. Once cancer spreads to the peritoneum, it is considered advanced or stage IV cancer^[2].

Primary peritoneal cancer has several specific types, including malignant peritoneal mesothelioma, which arises from the mesothelium of the abdomen. Other types include multicystic mesothelioma, leiomyosarcomas, and desmoplastic small round cell tumor^[3].

Areas of the Body Affected

The peritoneum covers and protects several important organs inside the abdomen. These organs can be affected when cancer develops in or spreads to the peritoneal membrane. The organs that the peritoneum surrounds include the bladder, intestines, rectum, and uterus^[1].

Cancer cells in the peritoneum tend to settle in specific areas where the peritoneal fluid naturally slows down or stops moving. These locations include the pelvic peritoneal reflections, the right and left paracolic gutters (the spaces between the colon and the abdominal wall), the upper part of the sigmoid mesocolon (the membrane that connects the colon to the back of the abdomen), the area around where the small intestine meets the colon, and the right subdiaphragmatic space (the area beneath the diaphragm on the right side)^[11].

• Bladder
• Intestines
• Rectum
• Uterus
• Ovaries
• Colon
• Stomach

Who is at Risk?

Women have a much higher risk of primary peritoneal cancer than men. Most people diagnosed with this condition are age 60 or older^[1]. The risk factors for peritoneal cancer are similar to those for ovarian cancer.

Having a first-degree family member such as a mother, sister, or daughter with peritoneal cancer, fallopian tube cancer, or ovarian cancer increases risk. People with BRCA1 or BRCA2 gene mutations, which are changes in genes that normally help prevent cancer, have a higher risk. Those with genes for Lynch syndrome, a hereditary condition that raises the risk of several types of cancers, are also at increased risk^[1].

Other risk factors include endometriosis, a condition where tissue similar to the lining of the uterus grows outside the uterus. Women who use hormone replacement therapy after menopause have an increased risk. People with obesity, those who are taller, and those with infertility or who have not had biological children may also face higher risk^[1].

For malignant peritoneal mesothelioma, asbestos exposure has been known for decades as a strong risk factor^[13].

Signs and Symptoms

People often don’t notice symptoms in the early stages of peritoneal cancer. Symptoms usually don’t appear until the cancer has progressed and affects a large portion of the peritoneum^[1][4]. This is one reason why most people are diagnosed at a later stage.

When symptoms do develop, they are often vague and can be confused with other, less serious conditions. The most common symptom is abdominal swelling or bloating. This happens because of fluid buildup in the belly, called ascites^[4]. A person may feel like they are gaining weight in the abdomen despite exercise. Women in menopause may appear as if they are pregnant^[4].

Other common symptoms include abdominal pain or discomfort, which is often described as vague cramping or pressure-like pain. Many people experience a loss of appetite and feel full quickly, even after eating small meals. Weight loss without trying is common. People often feel very tired, even after resting^[4].

Digestive symptoms may include nausea and vomiting, constipation, or diarrhea. Some people experience frequent urination. Abnormal vaginal bleeding, rectal bleeding, or an abdominal mass may also occur^[2][4]. As the disease progresses, shortness of breath and fatigue become more common^[2].

Complications can include bowel obstructions, sometimes requiring a stoma (an opening between the intestine and the outside of the body), and urinary tract obstruction due to tumors blocking the ureters, which may require a stent or nephrostomy tube (a tube from the kidney to the outside of the body)^[2].

How is it Diagnosed?

Diagnosing peritoneal cancer involves several steps. The healthcare provider will start by asking about symptoms and reviewing medical history. A thorough physical examination follows, including a pelvic exam to check for abnormalities in the uterus, vagina, ovaries, fallopian tubes, bladder, rectum, stomach, and colon^[7]. During the physical exam, the provider may be able to feel tumor nodules in the abdomen or detect fluid^[2].

Several imaging tests help visualize what’s happening inside the abdomen. A CT scan (computed tomography) is often the method of choice because it is available, cost-effective, and has relatively high sensitivity^[11]. An MRI (magnetic resonance imaging) can also be used, and its sensitivity depends on the size of peritoneal implants. For implants larger than 10 millimeters, MRI sensitivity is comparable to CT^[11]. A PET-CT scan may be the most sensitive method in some cases, though its usefulness in everyday practice is debated^[11]. Ultrasound has low sensitivity and specificity and plays only a marginal role^[11].

Blood tests are important diagnostic tools. The CA-125 blood test measures the level of a substance called CA-125, a tumor marker often found in higher amounts in the blood of people with ovarian cancer or peritoneal cancer. However, CA-125 can be elevated for other reasons, so this test alone cannot confirm a diagnosis^[7]. Other tumor marker tests may look for chemicals made by cancer cells^[9].

Peritoneal washing cytology is a test where fluid from the abdominal cavity is collected during a minor surgical procedure and examined under a microscope to check for cancer cells. Even when no visible cancer is present, a positive result is a strong sign that cancer has spread to the peritoneum^[9].

Staging laparoscopy is a minimally invasive surgical procedure used to look directly inside the abdominal cavity using a small camera. It allows healthcare professionals to inspect the peritoneum, find hidden tumors, and take tissue or fluid samples. This test is especially valuable for finding peritoneal cancer that is too small to be seen with imaging^[9].

A biopsy, where a sample of tissue is removed and tested in a lab, is often necessary to confirm the presence of cancer cells and determine the type of cancer^[1].

Healthcare providers may use the Peritoneal Carcinomatosis Index (PCI) during diagnosis. This scale assesses how much tumor is present in the peritoneum and helps map the location and size of tumors. The PCI serves as a communication tool between doctors and radiologists and helps surgeons plan treatment^[11][21].

Treatment Options

Treatment for peritoneal cancer depends on several factors, including whether the cancer started in the peritoneum or spread from elsewhere, how far the cancer has spread, and the patient’s overall health^[14]. A multidisciplinary team typically evaluates each patient, including surgical oncologists, medical oncologists, radiation oncologists, and other cancer care providers^[14].

The standard treatment for peritoneal cancer is often cytoreductive surgery (CRS) combined with hyperthermic intraperitoneal chemotherapy (HIPEC). Cytoreductive surgery, also called debulking surgery, is an operation to remove all visible cancer in the abdominal cavity, including any visible peritoneal tumors^[21][14].

After removing the tumors, the surgeon administers a heated chemotherapy solution, about 107 degrees Fahrenheit (approximately 42 degrees Celsius), directly into the abdominal cavity. The solution is gently circulated for about 90 minutes. Heating the chemotherapy improves how well tumor cells absorb the medication. This treatment can control symptoms, prevent cancer from returning, and in some cases, even cure the cancer^[14][21].

The HIPEC procedure is complex and can take six to nine hours. The average hospital stay after the procedure is seven to 14 days^[14]. The approach greatly enhances drug concentrations in the peritoneal cavity while decreasing systemic toxicity^[12].

Chemotherapy uses cancer-fighting medications to destroy cancer cells throughout the body. Medical oncologists may use chemotherapy before or after surgery. The first-line chemotherapy regimen for peritoneal cancer is typically a platinum agent with a taxane. If patients have BRCA1 or BRCA2 mutations, olaparib maintenance therapy may be recommended^[12].

Different chemotherapy regimens may include cisplatin plus pemetrexed, cisplatin plus paclitaxel, or mitomycin, doxorubicin, and irinotecan^[12]. Some approaches involve systemic chemotherapy, while others use intraperitoneal chemotherapy to deliver medication directly into the abdominal cavity.

Targeted therapy uses medications that attack specific abnormalities in or on cancer cells or boost the immune system to fight cancer. Doctors first test a patient’s cancer cells to determine whether a specific targeted therapy might work. This can be a treatment option for some patients with advanced primary peritoneal cancer^[1].

Radiation therapy uses high-energy radiation beams to destroy cancer cells. This noninvasive treatment may be recommended for patients with advanced primary or recurrent peritoneal cancer^[1].

Newer techniques include adding immunotherapeutic agents such as interleukins and interferons. Immune checkpoint inhibitors have been incorporated into treatment regimens for various solid tumors, including mesothelioma^[12].

While traditional therapeutic options have shown median survival ranging from 4 to 12 months, the application of multimodality therapy has shown promising results, with increased survival approaching 60 months^[12].

What to Expect

The outlook for peritoneal cancer varies depending on several factors, including the stage of cancer when diagnosed, the type of cancer cells involved, how well the cancer responds to treatment, and the patient’s overall health^[1]. Early detection and multimodal treatment offer the best chances for improved outcomes^[3].

Because peritoneal cancer is usually considered advanced or late-stage cancer, especially when it has spread from other organs, it is generally more serious than early-stage cancers^[21]. However, treatments can help slow disease progression and help people live longer.

People diagnosed with peritoneal cancer are usually older than those diagnosed with ovarian cancer. The prognosis for peritoneal cancer is also generally worse than that of ovarian cancer^[1].

For patients with peritoneal carcinomatosis who don’t have cancer spread outside the abdomen and who have good overall health, cytoreductive surgery combined with HIPEC is often recommended as first-line treatment. These approaches have significantly improved life expectancy for patients with peritoneal cancer^[11][13].

Although there is no cure for peritoneal carcinomatosis, surgery and specialized forms of chemotherapy help people with this disease live longer^[21]. The disease, while serious, continues to benefit from advances in treatment approaches.