Definition of RAI refractory cancer does not include the cervical lymph nodes (LN) radioiodine (RAI) uptake status. The aim of this study is to assess the outcome and the frequency of distant metastases (DM) and RAI uptake status in patients with non-RAI-avid metastatic LN compared with patients having RAI-avid metastatic LN.

A retrospective study of consecutive patients followed in Gustave Roussy institute between 1990 and 2015 who underwent at least one RAI therapy and one cervical LN relapse surgery with Proven pathology.

Finding Study cohort consisted of 145 patients [58.6 % females, median age at diagnosis of 38 years, papillary 135 (93 %), median follow-up of 14 years (2–42)]. All patients underwent total thyroidectomy and at least one RAI administration. Seventy-seven (53 %) patients disclosed uptake in neck LN (LN-RAI-pos) and 68 did not have any RAI uptake or disclosed a heterogeneous uptake (overall considered LN-RAI-neg). The risk of structural incomplete response at the last assessment was greater in LN-RAI-neg patients (38 %) compared with LN-RAI-pos patients (13 %) (p 0.0005). LN-RAI-neg was associated with an increased risk of DM compared with patients with LN-RAI-pos (35 % vs 18 % OR 2.4 95 %CI : 1.0747–5.715 ; p 0.024). The risk of occurrence of DM not disclosing RAI uptake was higher in the LN-RAI-neg group compared with the LN-RAI-pos group (58 % vs. 21 %, OR 89.4 95 %CI 6.1202–6154.8943 ; p<0.0002).

LN-RAI-neg status is significantly associated to a worse patient outcome and to the occurrence of DM and RAI-refractory DM.