Value of postoperative radiotherapy for thyroid cancer

A series of 405 patients with thyroid cancer treated by surgery with or without postoperative radiotherapy from February 1958 through 1979 is reported. The immediate evaluation of the operation was that it was either incomplete or complete. Incomplete surgery implied that there was (1) possible residual tumor in the operative field, the result of difficult dissection of the tumor off the neighboring organs or tissues, as assessed by the surgeon; (2) multiple (more than five) lymph nodes involved; (3) positive border of the removed lesions; or (4) microscopic evidence of tumor in the operative field. Complete surgery implied through extirpation of cancer grossly and microscopically. In 297 patients who had complete surgery, 238 patients treated by surgery alone had a 5-year survival rate of 92% (218/238), while 59 patients who received postoperative radiotherapy had a 5-year survival rate of 78% (46/59). The optimum dose of postoperative radiotherapy was 50-70 Gy in 5 to 8 weeks, with the spinal dose kept under 40 Gy. Our experience shows that postoperative radiotherapy did not improve the survival of patients who had had complete surgery. Yet, in 108 patients who had incomplete surgery, surgery alone yielded a 5-year survival rate of 33% (19/57), while surgery plus radiotherapy yielded a 5-year survival of 71% (36/51). Our observation shows a remarkable benefit with postoperative radiotherapy in patients who have had incomplete surgery (P less than 0.05). According to pathologic criteria, postoperative radiotherapy was more effective in well-differentiated cancers than in poorly differentiated ones. It was equally effective in untreated as well as recurrent lesions. The prognosis for younger patients was better, but the sex of the patients did not affect prognosis.