<prompt> Radiotherapy least useful in the primary management of-CA stomachCA esophagusCA cervixCA breast  <response>: 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. 