Extent of Stomach and Lymph Node Resection for Gastric (Stomach) Cancer
IntroductionGastric or stomach cancer is one of the most common cancers worldwide with the highest incidence in areas such as Japan, Korea, South America, and Eastern Europe. The incidence is much lower in the United States with about 22,000 new cases per year. The overall incidence of gastric cancer in the United States is decreasing, but cancers of the upper stomach and stomach-esophagus (gastroesophageal) junction are increasing. These tumors typically occur in people in their 60s and 70s, but can also occur in younger and older individuals.
The vast majority of gastric cancers are classified as adenocarcinomas, which are tumors arising from the inner mucosal lining of the stomach. These tumors grow from this inner lining and can spread to the deeper layers of the stomach. Eventually, tumors can penetrate the stomach wall and invade adjacent organs or spread along the peritoneum (the inner lining of the abdomen). In addition, gastric cancers can spread through lymphatic vessels to regional lymph nodes and though the bloodstream to the liver and lung. The goal of surgical resection of gastric cancer is to remove the involved stomach and regional lymph nodes before the tumor can spread to other sites.
Gastric cancers not classified as adenocarcinomas comprise only 5-10% of all gastric cancers. These cancers include lymphomas, gastrointestinal stromal tumors (GIST), and neuroendocrine tumors (carcinoids). The remainder of the information presented will be specific for gastric adenocarcinomas except as noted below.Diagnosis & WorkupClinicians at Massachusetts General Hospital have developed a standardized algorithm for the diagnosis and workup of gastric cancers.
Medical history and physical examination
The medical history is required to determine all symptoms, possible risk factors, and other medical problems. Physical examination is essential to rule out distant spread of disease.
The initial diagnostic test to identify a gastric cancer is an endoscopic examination of the stomach (upper endoscopy). Upper endoscopy can accurately identify abnormalities in the lining of the stomach, where gastric adenocarcinomas originate. An even more sensitive study is an endoscopic ultrasound, which combines an endoscopy with an ultrasound probe. This study can identify how deep the tumor has penetrated into the gastric wall and identify disease in regional lymph nodes.
The definitive diagnosis of gastric cancer requires a biopsy, which is performed at the time of upper endoscopy. Once the diagnosis is established, a workup is performed to determine if the cancer is localized or has spread to other sites. The most common sites of spread of gastric cancer are to regional lymph nodes, peritoneum, liver, and lung. Abdominal CT scans can often identify gastric wall thickening but overall is a relatively insensitive method of identifying gastric tumors. However, chest, abdomen, and pelvic CT scans are very useful for ruling out the spread of disease beyond the stomach.Laparoscopy
Gastric cancers can shed small deposits of tumor cells throughout the peritoneum, and this mode of spread is difficult to detect by any radiologic study. A procedure called laparoscopy is very sensitive in detecting peritoneal spread of tumor, and is often performed prior to surgical resection of gastric cancers. In this procedure, two or three tiny incisions are made in the abdominal wall, and a telescope and other small instruments are inserted into the abdomen.
Surgery remains the primary treatment modality for gastric cancer. Ideally, tumors should be removed with a margin of normal tissue of about 3-5 centimeters (about two inches). However, gastric cancers often arise in difficult anatomic locations and may require extensive surgical expertise to remove in their entirety with the best possible margin. Gastric cancers arising in the distal or lower portion of the stomach often can be removed without removal of the entire stomach (subtotal gastrectomy). Cancers arising in the proximal or upper stomach usually require removal of the entire stomach (total gastrectomy) and connection of the small bowel to the esophagus.
There is uniform agreement among gastric cancer specialists that the regional lymph nodes around the stomach should routinely be removed during resection of a gastric cancer and that at least 15 lymph nodes should be analyzed for adequate staging. This lymph node dissection is called a D1 lymphadenectomy. However, a recent large multi-center trial involving hospitals throughout the United States showed that the majority of patients (> 50%) did not receive even this minimum lymph node dissection.
There is ongoing controversy over whether a lymph node resection beyond a D1 lymphadenectomy is beneficial. Experienced gastric surgery centers, especially in Japan and Korea, have argued that a more extensive lymph node dissection that incorporates the next echelon of lymph nodes (D2 lymphadenectomy) improves staging and outcome in gastric cancer patients. The two largest Western trials examining this issue did not find a benefit to D2 lymphadenectomy. However, these studies had several flaws including a technique of D2 lymphadenectomy that unnecessarily included resection of the spleen and portion of the pancreas, leading to increased complications and mortality from surgery. A recently published randomized trial published in Lancet Oncology of 221 patients from Taiwan showed that overall survival was significantly higher in patients that underwent a more extensive lymph node resection compared to a D1 lymph node resection.
Several studies have demonstrated that the outcome of patients following surgery for gastric cancer is related to surgical experience and hospital volume. The surgical oncologists at the Cancer Center have all received specialty training in gastric cancer surgery and believe that gastric resection along with D2 lymphadenectomy can be performed safely and may improve survival in a subset of patients with gastric cancer. In addition, surgeons at Massachusetts General Hospital perform more surgeries for gastric cancer than any other hospital in New England.Chemotherapy and Radiation Therapy
Gastric cancers have the ability to spread to distant sites, most frequently to the peritoneum, liver, and lung. Chemotherapy may be beneficial to patients even if no sites of distant disease are identified in order to kill microscopic foci of tumor cells. If macroscopic distant disease is identified, chemotherapy may be beneficial in decreasing the growth and spread of disease.
Chemotherapy is usually given in combination with radiation therapy after surgical resection of the gastric cancer. A recent trial published in the New England Journal of Medicine showed that patients receiving chemotherapy and radiation therapy after surgical resection of gastric cancer had improved survival compared to those treated with surgery alone. However, this trial enrolled patients after surgical procedures with no quality control. Thus over half of patients received inadequate lymph node resections. There was no survival advantage in the subgroup of patients who received a D2 lymphadenectomy, although the number of patients in this subgroup was likely inadequate to form a definitive conclusion.
A recent trial (MAGIC trial) presented at the American Society of Clinical Oncology meeting in 2005 showed that patients who received a combination of epirubicin, cisplatin, and 5-fluorouracil (ECF) before and after surgery had improved survival compared to patients who underwent surgery alone. Currently, many patients at Massachusetts General Hospital are either receiving the ECF regimen outlined by the MAGIC trial or are entering a study randomizing patients after surgery to standard 5-fluorouracil and radiation therapy or ECF combined with 5-fluorouracil and radiation therapy.