GLOSSARY

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Glossary of Terms Regarding Peritoneal Malignancy

This list is not comprehensive. However, you’ll find these terms being routinely used in discussions concerning Peritoneal Malignancies. For more detailed explanations, please consult with your oncologist.

Towards the middle of this page you’ll find a more detailed description of Peritoneal Carcinomatosis.

Ascites is the pathologic accumulation of fluid in the abdominal cavity. Normally, there is a balance between fluid secretion and absorption in the peritoneal cavity. Ascites occurs when either the secretion rate increases or the absorption rate decreases disproportionate to the other. A variety of benign and malignant conditions could lead to the development of ascites.

Cytoreductive Surgery refers to the aggressive removal or destruction of all visible tumors present throughout the peritoneal surfaces. This can be accomplished by removal of or by destruction of the tumor using a combination of surgical techniques that include: electro-evaporation, laser, ultrasonic dissection and argon beam coagulator. The long-term results are directly related to the ability of the surgeon in the removal of all visible tumor. The long-term benefits of these procedures are directly related to the size of the deposits of residual disease. The smaller the size of the residual tumor deposits the greater the chance the tumor will respond to the chemotherapy. Cytoreductive Surgery is an extensive, lengthy procedure that lasts on average more than ten hours. Frequently, it is necessary to remove segments of small and large bowel, spleen, stomach and pancreas, to achieve adequate cytoreduction. The extent of resection will depend upon the location and size of the tumor, but considering the quality of life achieved for the patient.

Hyperthermia (High temperature) has several benefits in the treatment of these conditions. Heat increases the penetration of chemotherapy drugs into tissues, heat increases the cytotoxicity of some chemotherapy drugs. Heat has by itself an anti-tumor effect. The damage produced by heat is greater to cancerous cells than to normal cells.

Hyperthermic Intraoperative Intraperitoneal Chemotherapy (HIPEC) refers to the intraoperative administration of heated chemotherapy into the peritoneal cavity, at the time extensive removal of tumor has been completed (Cytoreductive Surgery). This technique permits the administration of high concentrations of selected drugs into the abdominal and pelvic surfaces. The drug makes contact with all the peritoneal surfaces of the tumor resected areas. In contrast, the efficacy of the administration of the intraperitoneal chemotherapy delivered several days or months after surgery is limited due to adhesion formation.

Peritoneum is the smooth transparent serous membrane that lines the cavity of the abdomen and is folded inward over the abdominal and pelvic viscera. The peritoneum provides a frictionless surface over which the abdominal viscera can freely move, and the mesothelial lining secretes fluid that serves to lubricate the peritoneal surfaces. Normally, approximately 100 ml. of clear straw-colored fluid is present in the peritoneal cavity of the adult. This fluid contains water, electrolytes and other solutes derived from the interstitial fluid of the neighboring tissue and from the plasma of adjacent blood vessels. It also contains proteins and a variety of cell types. The latter vary in their numbers, structure and type in different pathological conditions; hence, they are of diagnostic importance. Normally, the cells consist of desquamated flat mesothelial elements derived from the peritoneal surfaces, and of wandering macrophages, mast cells, fibroblast, lymphocytes and a small number of other leucocytes. Some of these cells, particularly the macrophages, can migrate freely between the peritoneal cavity and the surrounding connective tissue; material injected intraperitoneally may be ingested by these cells and transported to various sites in the body. The lymphocytes in the fluid provide both cellular and humoral, immunological defense mechanisms. The quality and quantity of this fluid may change with various pathological conditions.

Peritoneal Absorption: Substances in complete solution (solutes) are probably absorbed directly into the blood capillaries, whereas particulate matter in suspension probably passes into the lymph vessels, with the aid of phagocytes. The absorption of fluid is more or less equally rapid in all parts of the peritoneum. The greater absorption in the upper part of the abdomen is due to the larger area of the peritoneal surface in the subphrenic region and absorption is expedited by the respiratory movements in this region.

Peritoneal Cavity is the potential space containing the abdominal and pelvic viscera.

Peritoneal Carcinomatosis

Peritoneal Carcinomatosis refers to a wide variety of tumors that present with extensive peritoneal involvement with or without parenchymal involvement of solid organs such as the liver, spleen and lymph nodes. It is a common evolution of cancers of the digestive tract such as stomach, small bowel, colon, rectum, appendix and pancreas. Other tumors that may lead to these conditions include: mesothelioma, pseudomyxoma peritonei and sarcomas. In other patients, the tumor may arise from the peritoneum itself, giving rise to what is called Primary Peritoneal Surface Malignancy.

The initial dissemination of cancer occurs via three routes; the lymphatics, the portal circulation and the peritoneal surfaces. Although lymphatic and hematogenous metastases indicate an aggressive disease process, it is possible that dissemination to peritoneal surfaces may be only superficial contamination of the parietal and visceral peritoneum and may be treatable for a potential cure.

Peritoneal carcinomatosis has been regarded as a terminal condition; and most oncologists would consider it a condition for palliative treatment only, a means to make the patient comfortable until his/her death. Most of these patients present with debilitating ascites and/or intestinal obstruction, causing pain and terminal starvation. Without aggressive therapy, the survival of patients following this diagnosis is dismal; the majority will die within a few months. Sadeghi et al, reported on the natural history of these conditions if left untreated (Cancer 2000; 88:358-63). Mean and median overall survival periods were 6.0 and 3.1 months respectively. Survival rates correlated directly with the initial peritoneal carcinomatosis staging: survival was 9.8 months for Stage I with malignant peritoneal granulations less than five mm in greatest dimension, versus 3.7 months for Stage IV with large, malignant peritoneal masses more than two cms in greatest dimension. The mean survival for patients with gastric, colorectal, pancreatic and primary carcinoma were 6.5, 6.9, 2.9 and 2.9 months respectively.

Aggressive cytoreductive surgery with or without chemotherapy has been shown to be beneficial in several studies. First reported in the 1980s, intraperitoneal chemotherapy has been described as a safe treatment for peritoneal carcinomatosis and is currently under evaluation in several centers around the world. The administration of hyperthermic intraperitoneal chemotherapy at the time of surgery has added another option for the management of these conditions. New treatment strategies, including peritonectomy procedures and perioperative intraperitoneal chemotherapy, have achieved long-term disease free survival in this group of patients with terminal conditions.

Despite the aggressive nature of this combined therapy, it is generally well tolerated, with mild to moderate hematological toxicity being the most commonly associated result. Other complications related to the surgery may be significant, but in general can be managed by a specialized team that follows the patients closely during the postoperative period. The type of chemotherapy used depends on the type of tumor being treated. On follow-up, quality of life studies have demonstrated the recovery of normal activity in a significant number of patients. Long-term survival has been achieved in several studies.