Radiotherapy least useful in the primary management of-

Gastric cancer is generally radioresistant, and radiation therapy is therefore rarely indicated. Gastric adenocarcinoma is a relatively radioresistant tumor, and the adequate control of the primary tumor requires doses of external-beam irradiation that exceed the tolerance of surrounding structures, such as bowel mucosa and spinal cord. As a result, the major role of radiation therapy in patients has been palliation of pain. Radiation therapy alone after a complete resection does not prolong survival. In the setting of surgically unresectable disease limited to the epigastrium, patients treated with 3500-4000 cGy did not live longer than similar patients not receiving radiotherapy; however, survival was prolonged slightly when 5-fluorouracil (5-FU) plus leucovorin was given in combination with radiation therapy (3-year survival 50% vs 41% for radiation therapy alone). In this clinical setting, the 5-FU likely functions as a radiosensitizer.