The role of radioactive iodine in the treatment of advanced differentiated thyroid carcinoma.

OBJECTIVE: 131I therapy may be beneficial for patients with advanced differentiated thyroid cancer (DTC) but there have been relatively few studies of the prognostic factors which influence the outcome. We have evaluated differences in outcome in relation to histology, localization of tumour, differentiation grade, age and sex after 131I as the only secondary treatment for advanced stages of DTC. DESIGN: Retrospective study of a selected patient group treated according to a fixed protocol. PATIENTS: We studied the outcome in 86 patients with stage pN3, pT4 or pM1 out of total of 432 patients treated for DTC from 1970 until 1991. RESULTS: The overall cure rate of 131I therapy after a mean follow-up of 12.1 years was 50% (papillary 65% vs follicular 23%). The overall 5-year progression free survival (PFSR) was 66%. Three out of 11 patients with bone metastases from follicular cancer were cured after a mean dose of 13.2 GBq, significantly less than the average dose of 28.4 GBq given to all patients with bone metastases. In the univariate analysis of 5-year PFSR histology (papillary 79% vs follicular 43%), differentiation grade (well differentiated 81% and moderately differentiated 31%), tumour stage (pN3100%, pT4 77% and M1 48%), and age (< or = 60 years 85% vs > 60 years 46%) were significant prognostic factors. A multivariate analysis showed differentiation grade, histology and age to be significant prognostic variables for outcome (moderately vs well differentiated: RR = 3.16, follicular vs. papillary: RR = 2.56 and age > 60 vs age < or = 60: RR = 2.43). CONCLUSIONS: 131I can be an effective treatment in patients with advanced differentiated thyroid cancer at all sites and can cure, on average, 50% of all patients with advanced differentiated thyroid cancer.