c l i n i c a l
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d i s c u s s i o n
Gastric Cancer
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Gastric Cancer | ||
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Related narratives: Gastrectomy, Palliative Gastrectomy The incidence of gastric cancer has declined significantly in the United States over the past 50 years, but still results in approximately 14,000 deaths per year. Other countries, such as Japan, report a much higher incidence, possibly related to dietary factors. Gastric cancers are most commonly adenocarcinomas (95%), although lymphomas and smooth muscle tumors (GIST - gastrointenstinal smooth muscle tumors) do occur. Adenocarcinomas are subdivided into two groups, intestinal and diffuse. Intestinal tumors are more common in endemic areas and are associated with H. pylori infection. Bacterial overgrowth is thought to contribute to nitrate reduction, chronic inflammation, and mucosal atrophy. These changes eventually result in mutagenesis (via nitrite), dysplasia and then invasive carcinoma. The diffuse type of adenocarcinoma is more prevalent in Western countries and is associated with more proximal tumors. Diagnosis of gastric carcinoma centers on early endoscopy with biopsy of suspicious lesions, including gastric ulcers. Once the tissue diagnosis of adenocarcinoma is made, further evaluation consists of CT scan and endoscopic ultrasound. Both methods provide important staging information regarding the spread of the lesions, either by lymphatogenous or by direct invasion. Metastatic lesions are candidates for pallative therapy, either resection or bypass, and possible chemotherapy. Locally advanced lesions are considered for neoadjuvant therapy (see subtotal gastrectomy after neoadjuvant therapy) with restaging and consideration for resection. Resectable adenocarcinomas, those that do not penetrate the gastric wall, are candidates for curative resection. These patients are brought to the operating room for exploration after a thorough preoperative assessment of nutrional status (with preoperative feeding if needed). Exploration proceeds either laproscopically (with or without ultrasound) or open for confirmation of resectable disease. Lesions of the proximal two-thirds of the stomach are treated with a radical total gastrectomy with roux-en-y reconstruction. Extension into the right chest via thoracotomy is sometimes needed for complete mobilization of the distal esophagus. Tumors confined to the distal one-third of the stomach are treated with a radical subtotal gastrectomy (75% distal gastrectomy, removal of the proximal 3 cm of duodenum, removal of gastrocolic ligament and greater omentum). Reanastomosis is made with either a Roux-en-Y or Billroth II (gastrojejunostomy). Consideration is given to placment of a feeding jejunostomy. The extent of lymph node dissection for either location of tumors is limited to a D1+ lymphadenectomy, that is all nodes over the lesser and greater curvature, the right and left cardinal nodes, and the short gastric nodes. For node positive disease (based on pathological evaluation) consideration should be given to enrollment in a clinical trial for adjuvant chemotherapy. Gastric lymphomas are treated with resection for stage I and II lesions followed by chemotherapy. More advanced tumors are treated with chemotherapy and/or radiation. If tumor regression is seen, then resection is indicated. GISTs (formerly known as leiomyomas and leiomyosarcomas) are determined to be either benign or maligant based upon histological characteristics (> 5 mitotic figures per high power field). Small lesions (< 3cm) can be treated by complete exision with a margin of normal stomach wall. Larger lesions are treated with more formal resections (as above). With maligant lesions, recurrent disease occurrs in approximately 50% of cases and are sometimes resected on a case by case basis. Adjuvant therapy with either chemotherapy or radiation remains limited to clincial trials. Staging Primary Non-Hodgkin's Gastrointestinal Lymphoma
References Textbook of surgery: the biological basis of modern surgical practice.-15th ed. / [edited by] David C. Sabiston, Jr.; editor for basic surgical science, H. Kim Lyerly. Surgical attending rounds/ [edited by] K. Francis Lee, Cornelius M. Dyke - 2nd ed. Current Surgical Therapy.-6th ed. / [edited by] John C. Cameron. 1998.
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