The surgical treatment and prognostic factors of well-differentiated thyroid cancers in Chinese patients: a 20-year experience.

BACKGROUND

Well-differentiated thyroid cancers (WDTC) are usually slow-growing neoplasm with an indolent clinical course. Assessment of treatment modalities for them requires a long-term follow-up in a large population, and is still of much debate. A systematic analysis of the history, prognosis and therapy for this disease in Taiwan is lacking.

METHODS

A retrospective analysis of clinical and pathological records was conducted on 488 patients (149 male and 339 female, male: females = 1:2.28) treated for WDTC in the Veterans General Hospital-Taipei from 1971 to 1991 with subsequently follow-up until December 1994 (Mean follow-up: 8.5 years). Factors influencing recurrence, survival and different treatment were analyzed.

RESULTS

Papillary thyroid cancer increased obviously as compared to our experience from 1959-1976. Changing tumor behaviors, including increasing female/male ratio, higher percentage of papillary cancer, decreasing primary tumor size and lower distant metastatic rate at the time of initial diagnosis, were noted. Factors influencing survival, as determined by univariate analysis, included age, gender, distant metastasis, extrathyroidal invasion, tumor size, nodal involvement, histological type, extent of surgical therapy and use of postoperative radioactive iodine. Those patients aged more than 45 at initial diagnosis, with primary tumors larger than 4 cm, with extrathyroidal invasion, and with distant metastasis at initial diagnosis were classified as being at high risk. The others were at low risk. Total or near total thyroidectomy (TTx), depending on the judgement of each surgeon, had much higher complication rate than lobectomy with/without isthmusectomy, but offered no benefit effect on disease-free survival or overall survival rates. Postoperative radioactive iodine ablation treatment and thyroxine replacement in suppressive dose after TTX improved survival among high risk patients. Lobectomy with/without isthmusectomy in low risk patients, followed by thyroxine suppression therapy, was adequate to improve the postoperative outcome and with low complication rate. Lymph node resection in patients with clinically palpable nodes improved longterm prognosis.

CONCLUSIONS

Changing tumor behavior of WDTC leading to favorable prognosis has been noticed since 1971. Total or near total thyroidectomy is worthwhile in high risk patients with WDTC but does not appear necessary in low-risk patients. Lymph node dissection for metastatic lymph node could improve the survival rate.