Results of external beam radiotherapy in patients with well differentiated thyroid carcinoma.

Surgical, thyroid hormone and radioactive 131I therapy are the standard curative treatments for well differentiated thyroid cancer. However, for residual, recurrent and nodal involvement of well differentiated thyroid cancer, external radiotherapy may be important in preventing distant metastases. The postoperative treatment of well differentiated human thyroid cancer with external radiotherapy is controversial. We retrospectively reviewed the records of 699 patients with papillary or follicular thyroid cancer, of whom 72 received external radiotherapy treatment after surgery. Thirty-two of these patients were at clinical stage 2 or 3 at the time of diagnosis while 172 patients at clinical stages 2 or 3 did not receive external radiotherapy after surgery. The patients who received external radiotherapy were older than those who did not (42.9 +/- 14.5 vs. 38.6 +/- 15.3), although this was not statistically significant. There were no significant differences in clinical parameters including surgical methods employed, histopathological types of cancer, follow-up stages, postoperative thyroglobulin levels, tumor size, accumulated 131I doses and survival rates between the two groups. To clarify the effect of external radiotherapy in patients with local invasion, we compared the survival rates of the patients with clinical stage 3 in the two groups and again no significant difference was found. During the follow-up period, 21 (28.4%) of the 72 patients who received external radiotherapy died of thyroid carcinoma. In our limited period of study, external radiotherapy did not improve the survival rate of patients with well differentiated thyroid cancer, though it appeared to cause temporary tumor regression.