The role of postoperative adjuvant radiotherapy in the local control in medullary thyroid carcinoma.

Background: The value of postoperative radiotherapy in the treatment of medullary thyroid carcinoma (MTC) has not been unequivocally demonstrated. Therefore our study aimed to answer the question of whether adjuvant radiotherapy showed any impact on the risk of local recurrence and whether there were any differences in response to radiotherapy between hereditary and sporadic MTC.

Methods: A retrospective analysis involved 254 MTC patients, among them 73 patients with a hereditary disease. Two hundred and twenty-four patients, including 43 persons at high risk of local relapse, underwent only initial surgery, 18 other patients were operated due to MTC recurrences, whereas the remaining 12 patients had cytoreductive procedure or were not amenable for surgery. Radiotherapy was carried out in 132 patients. One hundred and twenty patients underwent adjuvant radiotherapy, among them 102 patients after initial surgery. The median follow up was 10 years (range 0.5-29 years).

Results: Local recurrence occurred in 107/254 patients, among them in 63 subjects after prior radiotherapy. The frequency of relapse showed significant, increasing trend toward higher MTC stages (p<0.001). More relapses were noticed in patients with lymph node metastases at diagnosis. Adjuvant radiotherapy was associated with a lower risk of nodal recurrence only in high-risk patients, particularly if lymph node metastases were present at MTC diagnosis. The differences between hereditary and sporadic subgroups were not significant.

Conclusions: Adjuvant radiotherapy has a limited importance in MTC treatment. It should be considered in high-risk MTC patients. The presence of RET mutation does not influence the response to radiation.