Efficacy of low and high 131I doses for thyroid remnant ablation in patients with differentiated thyroid carcinoma based on post-operative cervical uptake.

OBJECTIVE

The aim of this study was to determine the efficacy of low (1110 MBq (30 mCi)) and high (3700 MBq (100 mCi)) 131I doses on the ablation of post-surgical remnants in patients with thyroid cancer based on the measurement of post-operative cervical uptake.

METHODS

The study was conducted on 155 patients without metastases after thyroidectomy who received a 1110 or 3700 MBq ablative dose and who were assessed by pre-therapy cervical uptake. The patients were divided into six groups according to the uptake result and the dose received. Successful therapy was defined as a negative scan 6 months to 1 year after ablation.

RESULTS

Ablative therapy was successful in 90% of patients with uptake <2% who received the 1110 MBq dose (n=30) and in 92.5% of patients who received the 3700 MBq dose (n=40), P=0.95. In the group with uptakes ranging from 2% to 5%, successful therapy was observed in 65% of patients receiving 1110 MBq (n=20) and in 86.6% of patients receiving 3700 MBq (n=30), P=0.14. In patients with uptake >5%, a 46.6% success rate was obtained for the 1110 MBq dose (n=15), while efficacy was 70% in patients receiving 3700 MBq (n=20), P=0.16.

CONCLUSION

This study demonstrated the efficacy of low doses in patients with lower remnants after surgery (uptake <2%), the inverse correlation between uptake and ablation efficacy with low and high doses, and the usefulness of the measurement of cervical uptake for the definition of the ablative 131I dose.