Efficacy of I131 ablation therapy using different doses as determined by postoperative thyroid scan uptake in patients with differentiated thyroid cancer

PurposeThe optimal dose of I¹³¹ for ablation of functioning residual thyroid tissue after surgery is controversial. The current study was conducted to determine the optimal dose of I¹³¹ for remnant postoperative ablation. A review of the literature is included.Methods and materialsA total of 238 patients with papillary and follicular carcinoma were treated with I¹³¹ for ablation of a postoperative thyroid remnant. The I¹³¹ dose was based on the 24-h percentage of neck uptake in the postoperative thyroid scans. Patients with <5% uptake received a median of 85 mCi; 6–10% uptake, a median of 80 mCi; 11–15% uptake, a median of 60 mCi; 16–20% uptake, a median of 50 mCi; and ≥21% uptake, a median of 30 mCi. The ablation results were compared with the prognostic factors.ResultsComplete ablation was observed in 40 (92%) of 43 patients receiving 85 mCi, in 31 (94%) of 33 who received 80 mCi, in 39 (95%) of 41 who received 60 mCi, in 51 (93%) of 55 who received 50 mCi, in 37 (94%) of 39 who received 30 mCi, and in 18 (96%) of 19 who received 30 mCi. The overall successful ablation rate was 94% (95% confidence interval, 89–100%).ConclusionOur findings suggest that patients with differentiated thyroid cancer can be treated with doses of I¹³¹ according to the percentage of neck uptake of postoperative total body scan, with high complete ablation rates, without exposing patients to higher dose levels of I¹³¹.