randomized clinical trial comparing 50mCi and 100mCi of iodine-[131] for ablation of differentiated thyroid cancers

ABSTRACT

To compare the efficacy of low [50 mCi] and high dose [100 mCi] Iodine-131 in ablation of differentiated thyroid cancer remnants. Baseline serum thyroglobulin [sTg], thyroglobulin antibody [Tg Ab] and diagnostic whole body iodine scan with 2 mCi of I-131 were performed in each individual. After 6 months serum Tg, Tg Ab [of-thyroxin] and WB iodine scan with 10 mCi of I-131 were done to assess the efficacy of the low and high dose of I-131. Iodine ablative therapy [IAT] was considered successful [complete ablation] if the I-131 whole body scan was negative and sTg level was undetectable. In case of positive scan and/or sTg level detectable the patient was considered as unsuccessfully/partially ablated. In group A, [high dose] successful IAT was seen in 12/20 [60%] patients. Of these 5/7 [71%] had follicular Carcinoma on histopathology and 7/13 [54%] had papillary Ca. In group B, [low dose] successful IAT was seen in 8/20 [40%] patients, out of which 3/10 [30%] had follicular Carcinoma on histopathology and had successful IAT. 5/10 [50%] patients with papillary Carcinoma had successful IAT. As far as histopathology is concerned, in group A, response to high dose I-131 was better in follicular type than papillary type. Whereas in group B, response to low dose I-131 was better in patients with papillary type than follicular. 100 mCi of radioactive Iodine-131 [I-131] is a more effective therapeutic dose than 50 mCi [I-131] in the treatment of differentiated thyroid cancer remnants. Furthermore, follicular Carcinoma respond better to 100 mCi I-131 than 50 mCi while papillary Carcinoma showed an almost equal response to both