All T2, T3, some T1 with N1 (less than 5 mm and less than 5 lymphnode). Multifocal where the sum is more than 2 cm.

A meta-analysis by Fang Y et al. (J Endocrinol Invest. 2013. Radioiodine therapy for patients with differentiated thyroid cancer after thyroidectomy: direct comparison and network meta-analyses) could not clarify which activity of I-131 is the best in successful ablation rate. In addition, a final staging of thyroid cancer is only achieved by checking stimmulated Tg and negative post RIT WB scan.

As far as we do not know the best ablation activitiy, we ablate in agreement with German guidlines with 100 mci (exceptions are low-risk and specilally very-low risk DTC).

Only those within the so-called very low risk category. A recent report describes higher recurrence rates in patients receiving low dose RAI as compared to those receiving the usual 100 mCi dose

Dear Dr. Mercado, Thank you for your response. I am also interested in reviewing your mentioned report.

Controversy exist in this issue until large randomized trials with long term follow up was done. The dormancy of thyroid cancer makes work on this issue very difficult. You may have recurrences even 35 years after initial therapy. Anyhow, the proponents of 30mCi emphasis on complications of radio-iodine(adverse effect on salivary gland, lacrimal gland,...), radiation burden, admission costs to the patients and absence of superiority of 100mCi which is shown in the two well known published trials by Schlumberger and Mallick in NEJM. The opponents of 30mCi on the other hand, mainly emphasis on the short term follow up of those studies as well as absence of well controlled studies about complications of I-131. A meta-analysis in 2012 (ANTONIS VALACHIS, Acta Oncologica, 2012) showed that successful ablation is not different between 30 and 100 mCi, while complications are significantly higher in high dose group. ION study which is undergoing, compares iodine administration versus no Iodine in low and low to intermediate risk patients. We should wait for its results that is expected to be published next year.

I treat all patients with low risk(ATA classification) with 30mCi. Also we are running a randomized trial in intermediate risk patients comparing 30mCi Vs 150 mCi ( Young T2 N1 and T3N0 with low fTg and noninvasive histology).