Risk Factors and Prognosis of Recurrent Thyroid Cancer

Lee, Jun Hyuk; Jung, Jin Hyang; Hwang, Gyu Ha; Park, Ho Yong; Lee, Young Ha

Abstract

PURPOSE
Differentiated thyroid cancer is known to be one of cancers which have a favorable prognosis and long-term survival resulting from slow growth of tumor and late distant metastasis. Patients are nearly cured of thyroid cancer after first operation. But, some of those have high risk factors of recurrence. Practically it has been reported that 20% of those have recurrence of cancer and 50~60% of patients died of recurrence. We analyzed factors involving to recurrence after initial treatment, frequency and site of recurrence, disease-free interval, and results of treatment. Based on this information, we investigated therapeutics to decrease the rate of recurrence and prognostic factors to expect death.
METHODS
1803 patients were primarily operated for thyroid cancer in Kyungpook National University Hospital between 1985 and 2003. Among the cases, we reviewed the clinical records of 124 patients (6.9%) who had recurrent thyroid cancer. We analyzed the difference in frequency of recurrence on the basis of sex, age, histologic types, risk groups, and lymph node metastases when they had a first operation. The correlation between these factors and mortality rate was analyzed statistically by using Chi-square test and Fisher's exact probability test.
RESULTS
Post-operative recurrence of thyroid cancer was highly observed in over 40 years old at first operation (8.4% vs. 4.9%), men (17.1% vs. 3.9%). Similarly, in the case of medullary or poorly-differentiated thyroid cancers, the groups of patients with high-risk (12.3% vs. 3.9%) or with lymph node metastases (13.5% vs. 3.7%) have high frequency of recurrence. Among the 124 patients, 53.3% cases have regional recurrence sites and 20.1% have local, 17.7% distant metastases, and 1.6% combined locoregional. The number of patients who died of recurrent cancer was 32 of 124 cases. Major cause of the death was distant metastases. In the case of 104 patients who had recurrent differentiated thyroid cancer, significant prognostic indicators of low survival rates are age greater than 45 years, neck dissection at second operation and distant metastases.
CONCLUSION
In order to decrease the rate of local and regional recurrence in thyroid cancer, we conclude that complete resections of thyroid tissue and cervical lymph nodes have to be operated specially in the group with high-risk. Although adjacent organs are infiltrated, active treatment should be carried out. The treatment of most medullary or poorly-differentiated thyroid cancers which result in the death of distant metastases still remains to be studied.