What is peritoneal mesothelioma? Peritonectomy, cytoreductive surgery and HIPEC

What is peritoneal mesothelioma?

The peritoneum is an organ consisting of a two-layer membrane that lines the abdominal cavity and the organs within it. Peritoneal cancers include peritoneal mesothelioma, one of the rare cancers. The membrane called the peritoneum originates from the body’s mesothelial (mesothelium) layer; the mesothelial layer surrounding the lungs is called the pleura, while that surrounding the heart is called the pericardium. The most common cause of the mesothelial layer becoming cancerous is inhalation of small asbestos fibers, which is why the pleural form of the cancer is the most common; however, these fibers can also be swallowed in sputum. They may also migrate from the chest cavity to the abdominal cavity, causing tissue damage that leads to peritoneal mesothelioma.

What are the types of peritoneal cancer?

As with many solid/organ cancers, peritoneal cancers can be primary or secondary. Here, primary and secondary refer to where the cancer began. The names are not a measure of how serious the cancer is.

Primary peritoneal cancers

Primary peritoneal cancer begins and develops in peritoneal cells. The first condition that comes to mind when primary peritoneal cancer is mentioned is primary peritoneal carcinomatosis, and this cancer is closely related to epithelial ovarian cancer. Both are managed in the same way and have a similar outlook.

A rare type of primary peritoneal cancer is peritoneal mesothelioma, the subject of this article.

Secondary peritoneal cancers

Secondary peritoneal cancer usually begins in another organ in the abdomen and then spreads to the peritoneum (metastasis).

Secondary peritoneal cancer can begin in the following organs:

• ovaries
• fallopian tubes
• bladder
• stomach
• small bowel
• colon
• rectum

Secondary peritoneal cancer can affect both men and women. It is more common than primary peritoneal cancer.

For example, 15 to 20 percent of people with colorectal cancer are known to develop peritoneal metastases. Approximately 10 to 15 percent of people with stomach cancer develop metastases in the peritoneum.

When cancer metastasizes from its original site, the new site will have the same type of cancer cells as the initial site.

An overview of treatment for peritoneal mesothelioma

Survival rates for peritoneal mesothelioma tend to be poor. Approximately one-quarter of people receiving this diagnosis are known to live three years or longer. An appropriate treatment approach planned in experienced hands may extend life expectancy. If peritoneal mesothelioma is diagnosed early, there is a very limited possibility of a cure (complete recovery). The best way to achieve remission (extend the disease-free period) is complete or near-complete surgical removal of cancerous tissue.

What is peritonectomy?

Peritonectomy is a form of cytoreductive surgery. Cytoreductive surgery is any surgical procedure that removes cancerous tissue. The term peritonectomy specifically refers to removal of the peritoneum. The operation may also remove parts of organs containing cancerous tissue. Organs that may be affected include the small bowel, large bowel, gallbladder, liver, stomach, pancreas and spleen.

The operation is mainly aimed at relieving signs and symptoms. Although it is not always possible to remove the cancer completely with surgery, it may slow progression and achieve remission. Surgery is generally combined with chemotherapy to increase the possibility of remission and reduce the likelihood of postoperative recurrence. This combination may eliminate cancer cells that the surgeon could not safely remove or that remained too small during surgery.

What is hyperthermic intraperitoneal chemotherapy?

For peritoneal mesothelioma, Hyperthermic IntraPEritoneal Chemotherapy (HIPEC) is often used after the surgical procedure during the operation. HIPEC is a relatively innovative chemotherapy method that injects heated chemotherapy drugs directly into the abdominal cavity. This differs from traditional chemotherapy, which administers drugs intravenously (into a vein) and allows them to circulate throughout the body.

HIPEC has been proven more effective than standard chemotherapy in treating peritoneal mesothelioma. Some studies have found that treatment with HIPEC gives patients significantly longer survival times. This is a major achievement in treating a disease that was previously very difficult to manage. Increased survival after HIPEC is associated with the epithelial subtype of mesothelioma.

The importance of the peritoneal cancer index

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 peritoneal cavity is divided into 13 well-defined regions (see the figure below). In each of the 13 regions, the size of the largest tumor nodule is measured. If no tumor is visualized, that region receives a score of “0”. If the largest tumor nodule is smaller than 0.5 cm, the score is “1”. For tumors measuring between 0.5 cm and 5 cm, the score is “2”. For lesions larger than 5 cm, the score is “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 of all 13 regions, with a maximum score of 39 (13 × 3).

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

HIPEC or standard cytoreductive surgery?

The largest multi-institutional registry combining retrospective data on patients with peritoneal mesothelioma (PM) treated with cytoreductive surgery (SRC) and HIPEC at 29 clinical centers worldwide included 405 PM patients; various intraperitoneal chemotherapeutic agents were used during HIPEC, including cisplatin, mitomycin C and doxorubicin. In patients receiving HIPEC, median overall survival was 53 months, and one-, three- and five-year survival rates were 81, 60 and 47 percent, respectively. Prognostic factors associated with increased survival in multivariable analysis were epithelioid histological subtype, absence of lymph node metastases, complete or near-complete resection (i.e. completeness of cytoreduction score 0 or 1 and use of HIPEC.

What are the benefits of peritonectomy?

Peritonectomy and HIPEC have several goals. These procedures tend to be palliative, meaning that they aim to reduce symptoms, extend survival and provide the best chance of long-term remission. Curing peritoneal mesothelioma is a realistic goal; people with mesothelioma who have less tumor tissue have a better chance for a combination of peritonectomy and, now, HIPEC, resulting in long-term remission.

For most mesothelioma patients, this operation is used to extend life. For patients with very advanced cancer, one benefit of peritonectomy is relief of signs and symptoms. Removing or reducing tumors in the abdomen can reduce pain and bloating, allowing the patient to feel more comfortable.

Risks and complications

Peritonectomy followed by HIPEC is major surgery. Although less risky than the radical operations used to treat pleural mesothelioma, it may still have significant complications. Older patients or those with complex medical problems are more likely to have postoperative complications.

Possible postoperative complications include fistulas (perforations) from the bowel, leakage from sites where the bowel has been sewn together, excessive bleeding and intra-abdominal infection. Other complications are the same as those seen with any major operation, including blood clots and infections. Unfortunately, it is possible for a patient to struggle to recover from this operation only for the cancer to recur soon afterward.

Organ damage and the need for an ostomy

Whenever surgery takes place in the abdominal cavity, there is a small risk of injury to the bowel or urinary tract. When this cannot be surgically repaired, or there is significant tumor involvement in the abdomen, a procedure called an ostomy may be necessary. A stoma is a surgical intervention that diverts the digestive or urinary tract to the outside of the body. This procedure creates an opening called a stoma, connecting the small bowel, large bowel (colon) or ureter to the outside of the body and bypassing the normal routes through which waste leaves the body.

Ostomies are typically performed when the bladder or bowel cannot function normally because of tumor involvement. In rare cases, organ damage may occur as a complication of surgery. This is not a common complication, but any abdominal operation, including cytoreductive surgery, may cause damage requiring an ostomy. A stoma may be permanent or only temporary to allow the affected tissue to heal.

Living with an ostomy brings many challenges. Patients need an ostomy bag to collect stool or urine. A stoma has no valve to stop the flow, so patients cannot control the passage of waste from the body. Specialist ostomy nurses are an invaluable resource for providing a management plan that includes solving any problems that arise. Coping with complex changes in body image can be emotionally difficult. These may be temporary or permanent. If stomas need to be closed, or closure is planned, another operation will be required.

Patient selection and the postoperative period

Recovery from cytoreductive surgery plus HIPEC varies from patient to patient. Younger, healthier patients and those with earlier-stage cancer typically recover faster and with fewer complications. Patients should stay in hospital after surgery and HIPEC chemotherapy if there are any complications. Patients may receive intravenous medications and fluids after surgery. Initially, a nasogastric tube is generally present to drain the stomach until normal bowel function returns. The aim is to resume oral feeding as soon as possible. Having a nutrition specialist can be very helpful in providing new dietary recommendations. After going home, patients will modify their activity until they have fully recovered.

Summary

Peritoneal mesothelioma is a serious and aggressive cancer. The prognosis (disease course) is generally poor, but innovative treatment options have improved survival times. Cytoreductive surgery, including peritonectomy followed by HIPEC, is an effective way to help patients live longer. For some, this approach may even provide a cure (complete recovery). If you are being treated for peritoneal mesothelioma, explore your treatment options. Your medical team can help you understand the risks and benefits of these aggressive treatments for peritoneal mesothelioma.

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Who is Paul Sugarbaker?

The article above was compiled from an article by Prof. Dr. Paul Sugarbaker, one of the world’s leading surgical oncology experts, entitled "Peritonectomy / Cytoreductive Surgery" on mesothelioma.net. Dr. Sugarbaker specializes in the surgical treatment of gastrointestinal cancer, peritoneal mesothelioma and peritoneal metastases. He developed an important treatment procedure for peritoneal cancers and metastases known as HIPEC. The innovative strategy uses surgery followed by circulation of heated chemotherapy drugs within the abdomen. Dr. Sugarbaker currently heads the Peritoneal Surface Malignancy Program and the Center for Gastrointestinal Malignancies at Washington Hospital Center. He also works at Sugarbaker Oncology Associates, a private practice.