Should patients with remnants from thyroid microcarcinoma really not be treated with iodine-131 ablation?

Remnant ablation by radioiodine is generally not recommended in patients presenting uni- or multifocal cancer <1 cm, in the absence of other higher risk features. We retrospectively studied low-risk patients (pts) with differentiated thyroid cancer (DTC) less than 1 cm recruited for radioiodine therapy (RAI).

91 pts (79 women, age 48.4 ± 12 yrs) with DTC were enrolled for RAI. Patients underwent pre-therapy ultrasonography (US), those with suspected/ambiguous lymph-nodes were excluded and proposed for cytology. Treated pts underwent post-therapeutic whole body scan (WBSt) completed by neck/chest SPECT/CT, when necessary (e.g. evidence of uptake outside of thyroid bed). A target lesion on SPECT/CT was defined as an identifiable lymph-nodal site presenting a matched significant iodine uptake. The patients were followed up for 14 ± 2 months thereafter.

All pts/cancers were pT1. The mean histological diameter was 0.68 ± 0.23 cm. Six patients were excluded because of suspected nodal involvement at US. Thirty (35 %) out of 85 pts had suspicious WBSt as per lymph-nodal involvement which was confirmed at the subsequent SPECT/CT acquisition in most part of pts (26/30; 86 %). Overall detected target lesions was 34, and nine (26 %) had interim positive fine needle cytology.

a significant part of low risk DTC patients, for whom RAI is not recommended, presents an incidental suspicion of lymph-nodal involvement at WBSt confirmed by subsequent SPECT/CT. Such setting would have not been treated by I-131.