Delayed 131-I First Treatment After Surgery has No Impact on the Median Term Outcome of Patients with Intermediate Risk Differentiated Thyroid Cancer

Objective: In intermediate risk DTC (IR-DTC) patients, selective use of radioiodine (131-I) for remnant ablation and/or as adjuvant therapy (RRA) is advocated. The recently suggested post-operative evaluation could delay the RRA. The aim of this study was to evaluate if a delayed RRA, can worsen the clinical outcome of IR-DTC patients. Patients and methods: 414 consecutive IR-DTC patients were divided according to the time elapsed from surgery to RRA, < 6 months (Group A - 186/414 [44.9%]) or ≥ 6 months (Group B - 228/414 [55.1%]). Clinical and biochemical data were collected, and clinical outcome was analyzed at the first evaluation after RRA (first-EV) and after a median of 6 years of follow-up (last-EV). Results: No difference in the clinical outcome of Group A and B was found. Since a different activity of 131-I could have an impact on the outcome, we separately analyzed the groups according to the 131-I activity [low-activity group:1,110MBq/30 mCi (n=320) and high-activity group: 3,700MBq/100 mCi (n=94)], further subdivided according to the time elapsed from surgery to RRA. No major differences were found in both low and high activity-groups when comparing the features of their subgroups A and B as far as in their clinical outcome. Conclusions: The time elapsed between surgery and the first 131-I treatment does not influence the clinical outcome of IR-DTC patients. This finding allows a more relaxed attitude in the decision making to perform or not the RRA in those IR-DTC cases in which a selective use of 131-I is recommended.