Endocrine Abstracts

JOINT4007

Objectives: Structural incomplete response (SIR) to treatment, characterized by persistent or recurrent disease, is observed in 2 - 6% of low-risk differentiated thyroid cancer (DTC) cases and in 67 - 75% of high-risk cases. For locoregional recurrence, surgery remains the optimal treatment when the smallest dimension of the targeted lesion is at least 8 mm in the central compartment or 10 mm in the lateral compartment. However, in cases with smaller lymph nodes, contraindications to surgery, or when the patient declines reoperation, alternative approaches such as active surveillance (AS) or minimally invasive treatments (MITs), like radiofrequency ablation (RFA) may be considered. The aim of this study is to evaluate the safety and efficacy of RFA in DTC patients with SIR.

Methods: It is a retrospective study of eight DTC patients with SIR confirmed by ultrasound (U/S)-guided fine-needle aspiration cytology (FNAC) and measurement of Thyroglobulin (Tg) in the washout fluid. Fourteen malignant lesions were ablated by radiofrequency (RF). We assessed the volume of each lesion, serum Tg and Anti-Tg antibodies and calculated the volume reduction ratio (VRR) prior RFA and then at one month, three months and subsequently every three months.

Results: Patients were followed for a mean period of 14.75 months (range: 4–24) after RFA was performed. The targeted lesions reduced significantly from a median volume of 0.24 mL (range: 0.09 - 0.9) to 0.01 mL (range: 0 - 0.03) (P < 0.05), with a median volume reduction rate (VRR) of 96.5% (range: 87 - 100%). Out of the 14 lesions that were ablated, 4 (28.6 %) were no longer visible on the U/S. Volume reduction was accompanied by a significant biochemical response, with a decrease in serum thyroglobulin (Tg) levels from a median of 1.05 ng/mL to 0.13 ng/mL (P < 0.05). In one patient with an aggressive radioiodine (RAI)-refractory histological variant, re-recurrence was documented, which was successfully treated with repeat RFA. Two patients developed Horner syndrome as a complication of RFA, but in both cases it was fully resolved within six months.

Conclusions: RFA may be considered as an effective and safe MIT in selective DTC patients with SIR, especially in cases of smaller lesions. Additional prospective studies, including aggressive DTC histological variants are needed towards tailored-made therapy.