Does remnant from differentiated thyroid micro-carcinoma patients really not be treated with Iodine-131 ablation?

Full text of publication follows. Aim: Remnant ablation by radioiodine is generally not recommended in patients presenting uni- or multifocal cancer <1 cm, without 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). Methods: 91 pts (79 women, age 49.4 ± 10 years) with DTC were recruited for RAI. Pts 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. Patients were followed up for 13 ± 2 months thereafter. Results: All pts/cancers were pT1. Mean histological diameter was (0.66 ± 0.25) cm. Six patients were excluded because of clear nodal involvement at US. Thirty (35%) out of 85 pts had suspicious WBSt as per lymph-nodal involvement which was confirmed at the following SPECT-CT acquisition in most part of pts (25/30; 83 %). Overall detected target lesions was 34, ten (29%) had interim positive fine needle cytology. Conclusions: a significant part of low risk DTC patients, for whom RAI is not recommended, presents an incidental evidence of lymph-nodal involvement at WBSt confirmed by SPECT-CT, when performed. Such setting would have not been treated by I-131. Indications for RAI in DTC low risk patients could be revised at least considering a different dimensional cut-off for the primary lesion. (authors)