<prompt> Most radiosensitive tumor isRenal cell carcinomaCarcinoma colonHepatocellular carcinomaTesticular seminoma  <response>: Ref Robbins 8e p989 In general, radiation therapy is mainly used for patients with seminoma, which is very sensitive to radiation. Sometimes its used after orchiectomy the operation to remove the testicle and is directed at the lymph nodes at the back of the abdomen the retroperitoneal lymph nodes. This is to kill any tiny bits of cancer in those lymph nodes that cant be seen. It can also be used to treat small amounts of seminoma that have spread to the nodes based on changes seen on CT and PET scans. 