Delayed radioiodine remnant ablation (RRA) does not impact on the outcome of intermediate risk for recurrence differentiated thyroid cancer patients (IR-DTC).

Selective use of 131I was advocated by ATA guidelines for IR-DTC. The post-operative evaluation, 3-4 mths after total thyroidectomy, should be considered in the decision making to perform or not RRA. However, the available data on the impact of delayed RRA on the outcome of IR pts, are conflicting. We retrospectively evaluated the data of 311 consecutive IR-DTC pts followed at our institution for a median of 5.9 yrs. All patients performed RRA with 30 mCi after rhTSH. We divided pts in Group- A (RRA <6 mths from surgery – 101 pts) and Group-B (RRA ‡6 mths from surgery – 210 pts). The median time elapsed between surgery and RRA was 3.4 mths in Group-A and 7.3 mths in Group-B. The two Groups were similar for gender distribution (female 75.6 vs 67.6% - p = 0.17) and age (median 44.7 vs 47.1 yrs – p = 0.18). Classic variant PTC (43.6 vs 42.4%), follicular variant (10.9 vs 14.8%), FTC (5 vs 4.3%) and aggressive variants PTC (40.6 vs 38.6%) were similarly distributed in Group-A and B (p = 0.821), as well as tumor dimension (median 2.2 vs 2 cm – p = 0.5), multifocality (55.4 vs 53.3% - p = 0.73), lymphnode metastases at histology (26.7 vs 27.6% - p = 0.87). At the first control after RRA (median 7 mths), no difference in Excellent (58.2 vs 62.3%), Biochemical (7.1 vs 5.8%), Structural (6.1 vs 5.8%) and Indeterminate Response (28.6 vs 26.1%), were noted (p = 0.91). At the end of follow-up (median 5.9 yrs), there were no difference in Excellent (74.5 vs 76.9%), Biochemical (2 vs 2.4%), Structural (10.2 vs 7.7%) and Indeterminate Response (13.3 vs 13%) [p = 0.9], as far as in the number of repeated 131I courses performed during the follow-up [p = 0.67]. 1) In IR-DTC pts, RRA performed <6 mths or ‡6 mths showed the same efficacy, both at the first control after ablation and at the end of follow-up; 2) No difference in the total number of 131I courses were noted between the two groups; 3) IR-DTC could critically and safely reassessed in the year following the surgery before deciding to perform RRA.