Ablation outcome post a high second ablative dose of radioactive iodine (I131) in patients with papillary thyroid cancer

Objectives Introduction: Post-operative complete remnant ablation (CRA) in patients with papillary thyroid cancer (PTC) was considered an independent variable that reduces loco-regional recurrence, remote metastases and cancer death. No single study reported 100% ablation rate post first ablation dose. Patients who failed to be completely ablated need a second ablation dose to achieve CRA. Aim: To assess ablation outcome post a second high ablative dose of I131 after failure of first ablation one of 100 mCi in patients with PTC.

Methods 49 patients with PTC (T1, T2, N0, M0) post total thyroidectomy who failed to achieve CRA post first ablation dose of 100 mCi were included in the current study. All patients received a high dose I131 re-ablation therapy (23 received 80 mCi, 21 received 100 mCi and 5 received 120 mCi). Six months later I131 whole body scan (WBS) and unsuppressed serum thyroglobulin level (Tg) were performed.

Results The 49 patients (4 males and 45 females) had an age range of 21-69 years. WBS was normal with unsuppressed serum Tg < 2 ng/ml post second ablation dose, confirming CRA,was found in 38 patients (77.6%). In the remaining 11 patients (22.4%), WBS showed small residual functioning thyroid tissue in the neck with Tg >2 ng/ml.CRA was achieved in 73.9% (17 out of 23 patients), 80.9 % (17 out of 21 patients), and 80% (4 out of 5 patients), post 80 mCi, 100 mCi and 120 mCi of I131 as a second ablation dose respectively, the difference is statistically insignificant (P>0.05).

Conclusions High second ablative I131 dose ,post failure of 100 mCi first ablation dose, achieves CRA in 77.6% of patients with PTC. This figure is 73.9%, 80.9% and 80% for re-ablation doses of 80mCi, 100 mCi and 120 mCi I131 respectively; with statistically insignificant difference.