What is peritoneal cancer
The peritoneum is the largest membrane in the body: it lines the inside of the abdomen, covering and protecting all the organs it contains (intestine, liver, stomach and ovaries, among others). Made up of epithelial cells, the peritoneum produces a fluid that helps organs move smoothly within the abdomen. Peritoneal cancer is rare and is not the same as bowel or stomach cancer. It is also not to be confused with cancers that have spread to the peritoneum.
For the most part, it starts in the lower part of the abdomen, known as the pelvis, where the ovaries are located. For this reason, primary peritoneal cancer and ovarian cancer behave very similarly and are often treated in the same way.
This type of cancer almost exclusively affects postmenopausal women (about 70% of women are diagnosed at advanced ages). Peritoneal cancer can occur anywhere in the abdominal space.
Peritoneal cancer subtypes
This type of neoplasm can be primary or secondary, designations that refer to the site of cancer onset and have no relation to severity.
- Primary – Primary peritoneal cancer starts and develops in the peritoneum, mostly affecting women. In men it is rare. Primary peritoneal cancer is closely related to epithelial ovarian cancer;
- Secondary – Secondary peritoneal cancer starts in another organ in the abdomen and then spreads to the peritoneum. It usually starts in the ovaries, fallopian tubes, bladder, stomach, small intestine, colon, rectum, or appendix. It can affect both men and women and is more common than primary.
It is estimated that between 15% and 20% of people with colorectal cancer will develop metastases to the peritoneum, while 10% to 15% of patients with stomach cancer tend to spread to the peritoneum.
Symptoms and signs of peritoneal cancer
Symptoms of peritoneal cancer are vague, and by the time they occur, the disease has already progressed. Many of the following signs are caused by fluid buildup (ascites) in the abdomen:
- Abdominal discomfort (indigestion, pressure, bloating or cramping)
- Feeling full even after a light meal;
- Nausea or diarrhea;
- frequent urination;
- loss of appetite;
- Unexplained weight gain or loss;
- Vaginal bleeding;
- Rectal bleeding;
- Shortness of breathe;
- Increase in abdominal volume.
Diagnosis of peritoneal cancer
It can be difficult to detect peritoneal cancer in the early stages. It is often only found during surgery to remove a known tumor elsewhere in the abdomen.
After the clinical examination, the doctor will order a series of tests to define a diagnosis. The main ones are:
- Imaging tests – are useful in the evaluation of patients with symptoms suggestive of peritoneal carcinomatosis. Computed tomography or MRI of the abdomen and pelvis can confirm the presence of new or recurrent disease in the peritoneum. They are also done to assess the extent of the disease in the abdomen. PET Scan can also be done to determine if the disease has spread outside the abdominal cavity, such as the lungs;
- Laparoscopy/Biopsy – Laparoscopy is performed to confirm the diagnosis and determine if a patient is a candidate for surgery. It is a minimally invasive procedure where, through small incisions, samples of the tumor are removed and sent to the pathologist for confirmation of the diagnosis (biopsy). Fluid from the abdominal cavity may also be collected to check for cancer cells. The procedure is useful for assessing the extent of disease in the peritoneal cavity; and
- Laboratory tests – blood tests may be done to look for substances that may be elevated in peritoneal cancer, such as CA 125. If levels are high, there may be peritoneal or ovarian cancer. Because CA-125 can be high for other reasons, the blood test alone does not confirm the diagnosis. Another more recent tumor marker considered in the exams is HE4, which is still little used.
The decision on the best treatment for peritoneal cancer depends on factors such as the stage and grade of the cancer, its size and its location. The patient’s age and general health also count.
Treatments for peritoneal cancer include:
- Surgery – in addition to helping with diagnosis, it can also remove tumors. Depending on what is found, other tissues and organs may be removed during the procedure – the surgeon may remove the visible parts of the disease and remove the ovaries, fallopian tubes and uterus;
- Chemotherapy – Drugs for treating peritoneal cancer are given by injection every week or every two to three weeks. Chemotherapy is sometimes given directly into the abdomen through a catheter placed under the skin during surgery. This is called intraperitoneal chemotherapy;
- Radiotherapy – treats cancer using high-energy X-rays to destroy cancer cells. Radiotherapy is only rarely used in the treatment of primary peritoneal cancer;
- Targeted therapy – can be used in some cases with drugs that aim to fight cancer cells without harming normal cells. Such targeted therapies include monoclonal antibodies, which target substances in cancer cells that promote their growth. They can be combined with chemotherapy.
The causes of peritoneal cancer are not well defined. What is known is that, in some cases, it develops because cancer cells from other organs reach the layer that lines the abdomen through the bloodstream and multiply, giving rise to the tumor.
Risk factors that may be related to the development of peritoneal cancer in women are the use of hormones after menopause, the presence of endometriosis and obesity.
Women at risk of ovarian cancer are also at increased risk of peritoneal cancer. This is even more likely if the patient has both the BRCA1 and BRCA2 gene mutations. Advanced age is another risk factor for peritoneal cancer.
One preventable factor that increases the risk of peritoneal tumors is exposure to asbestos (trade name for asbestos). Avoiding it, therefore, can be a way to prevent the disease.