Radioiodine therapy of differentiated thyroid cancer

Radioiodine (I-131) therapy has been in use for the treatment of thyroid diseases for the past six decades. However its use in therapy for well-differentiated thyroid cancer is still controversial. This is because thyroid cancers are generally slow growing tumours, with low mortality and normal survival. Long term follow-up studies for two to three decades to record recurrence and mortality and to establish definite conclusions on the acceptable modes of treatment are recommended. As the incidence of the disease is very low, a large number of cases to establish good statistical data is required. Most published reports deal with a small series of cases and hence are not statistically significant. In order to overcome these deficiencies, reports are now being published on collated data obtained from several centres. Here again the problems encountered are the differing protocols for treatment with radioiodine, the indications for treatment which may include or exclude ablation of residual thyroid tissue, cervical nodal metastases and distal metastases. The administered doses of radioiodine for ablation of residual thyroid tissue and metastatic disease also vary from centre to centre. The most reliable conclusions regarding treatment protocol encountered in radioiodine treatment are obtained from studies reported on a large series of patients followed over a period of 3 decades or more from a single institute with a more or less unchanged protocol of treatment. Such studies are few. These reports from a handful of centres around the world are the most referred and cited studies. This paper portrays a comprehensive global practice of radioiodine therapy of differentiated thyroid carcinoma, along with some practical aspects of the treatment and a few pertinent information based on the local experience at the Radiation Medicine Centre, Mumbai, which probably has one of the largest experiences in this aspect of thyroid cancer management in the world. (author)