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Thursday, May 10, 2007

Peritoneal Treatments

Peritoneal Surgery

While it is the primary tool for treating peritoneal mesothelioma, surgery, by itself, is not considered curative. The abdomen is a complex space, filled with a variety of easily damaged and extremely important organs. A cancer affecting the abdominal lining, or peritoneum (paira-tin-e-um) is therefore a very serious and hard to treat matter.

The peritoneum is made of two parts, the visceral and parietal peritoneum. The visceral peritoneum covers the internal organs and makes up most of the outer layer of the intestinal tract while the parietal peritoneum covers the abdominal cavity.

While both the pleural (chest) and the peritoneal (abdominal) space contain the same lining and suffer from the same cancer, the nature of the two spaces dictates that different treatment strategies must be used. The peritoneum is located in an area of soft tissues, easily accessed and pliable, where the pleura is found inside a rigid space (the rib cage) and is difficult to reach without cutting through bone. Thoracic (chest) surgery to remove the pleura almost always involves the permanent removal of at least one rib.

The peritoneal and pleural mesothelial cells are designed to provide lubricating secretions which allow the organs in each respective space to move freely. When the cells of the mesothelium malfunction due to the cancer's progress, an overproduction of this fluid often results. This is called ascites and causes many of the symptoms discussed earlier in the diagnostic section.

Unique structures inside the abdomen make treating peritoneal mesothelioma both more difficult and, in some ways, easier than pleural mesothelioma. There are two folds of the peritoneum called the greater and the lesser omentum. These structures serve to connect the viscera and provide support for blood vessels.

In most mammals, the great omentum forms a great sac, which is attached to the transverse colon and the stomach. It is loaded with fat, and covers nearly all of the intestines. The lesser omentum connects the stomach and liver and contains the hepatic vessels. There is also a ligament called the gastrosplenic omentum which connects the spleen and stomach. If the omentum is heavily encrusted with mesothelioma it may be necessary to remove it, changing the structure of the abdominal space quite dramatically.

On a comparative basis, therefore, the abdomen has a much larger surface area than the chest to be treated. Using a geographic analogue the chest is like a smooth coastline and the abdomen is like a coast covered with inlets and islands. The latter offers far more miles of coastline than the former. This, together with the complexity of the space and fragility of the organs such as the bowels, leaves little chance for surgically resecting all of the tumor.

The relative ease of access to the abdomen has numerous interesting benefits, however. The stomach wall can easily be entered to allow access to the abdominal space and this means that the area can support multiple debulking surgeries and inspections to keep the tumor in check. It also means that the area can be treated with innovative techniques such as heated chemoperfusion, gene therapy, immunotherapy and photodynamic therapy.

Consequently, a very successful strategy for treating peritoneal mesothelioma has emerged that combines aggressive debulking of the tumor with one or more of the other techniques as adjuvants.

Several treatment centers now offer peritoneal treatment that involves several courses of surgery over a specific interval, with chemotherapy, radiation or other treatments either during or after the surgeries. Success with this approach has been excellent and there are now a number of long term 7+ year survivors of peritoneal mesothelioma as proof of the value of this multimodality approach.

The technique of using heated chemoperfusion to attack the residual mesothelioma tumor in the abdominal space was pioneered by the peritoneal surgeons and then was applied to the pleural mesothelioma environment where the strategy is also meeting with success and extended survival times.

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