Radiation treatment parameters in the adjuvant postoperative therapy of gastric cancer

Radiation therapy will be used much more commonly in the treatment of adenocarcinoma of the stomach because of the results of the Intergroup Trial demonstrating an advantage to adjuvant postoperative chemoradiation therapy. Previous descriptions of radiation fields have not emphasized the variation in local spread patterns between tumors located in different portions of the stomach and the varying extent of the primary tumor and lymph node spread. Based on data obtained from surgical and pathologic series, we have recommended a variation in the radiation fields from those routinely applied at the present time. Tumors located primarily in the region of the gastric cardia have the highest risk of nodal involvement in the pericardial region and along the lesser and greater curvature, as well as risk of spread into the periesophageal tissue. However, there is a lower risk of involvement in the distally located nodes, especially in the gastric antrum, periduodenal, and porta hepatis regions. For a patient who has been well evaluated both surgically and pathologically, and found to be node negative, it may not be necessary to treat the nodes in these lower risk sites. Similarly, tumors that originate in the distal stomach, in the region of the gastric antrum, have a high likelihood of spread to the periduodenal, peripancreatic, and porta hepatis nodes, and a lower likelihood of spread to the nodes near the cardia of the stomach, the periesophageal and mediastinal nodes, or to the splenic hilar nodes. Any tumor originating in the stomach has a high propensity of spread to nodes along the greater and lesser curvature, although they are most likely to spread to those sites in close anatomic proximity to the primary tumor mass. Based on such information, we have described the nodal and primary sites that should be treated for different T- and N-stage tumors located in the cardia, body, or antrum of the stomach. These should be used as guides for defining appropriate field arrangements for the adjuvant postoperative therapy of gastric cancer.