Do radioiodine-avid lymph nodes from differentiated thyroid cancer on the initial posttherapy scan need repeated 131 I therapy?

• Published in: Frontiers in endocrinology (Lausanne) Vol. 14; p. 1099449
• Main Authors: Jiang, Yongji, Liu, Simin, Qiu, Xiaotong, Huo, Yanlei, Zhang, Xiaoying, Cai, Haidong, Lv, Zhongwei, Ma, Chao
• Format: Journal Article
• Language: English
• Published: Switzerland 2023
• Subjects: Adenocarcinoma - pathology; Humans; Iodine Radioisotopes - therapeutic use; Lymph Nodes - diagnostic imaging; Lymph Nodes - pathology; Retrospective Studies; Thyroid Neoplasms - diagnostic imaging; Thyroid Neoplasms - pathology; Thyroid Neoplasms - radiotherapy; 131I therapy; treatment response; posttherapy scan; differentiated thyroid cancer (DTC); lymph node metastasis
• ISSN: 1664-2392; 1664-2392

Residual/recurrent lymph node metastase (LNM) is often found after differentiated thyroid cancer (DTC) surgery. This study aimed to investigate whether patients complicated with radioiodine-avid ( I+) lymph nodes from DTC on the initial posttherapy scan (PTS) need repeated I therapy. From June 2013 to August 2022, DTC patients with I+ lymph nodes on the initial PTS who received at least two cycles of I therapy were retrospectively enrolled. They were divided into a complete response (CR) group and an incomplete response (IR) group according to their response to the initial I therapy based on the 2015 American Thyroid Association (ATA) guidelines. A total of 170 DTC patients with I+ lymph nodes on the initial PTS were included; 42/170 (24.7%) patients were classified into the CR group and 128/170 (75.9%) were classified into the IR group according to their response to the initial I therapy. None of the 42 CR patients had disease progression at the subsequent follow-up, and 37/170 (21.8%) IR patients improved after repeated therapy. Univariate analysis showed that N stage ( 0.002), stimulated thyroglobulin (sTg) level before initial I therapy ( <0.001), LNM size ( <0.001), number of total residual/recurrent LNM ( 0.021), radioiodine-nonavid ( I-) LNM ( 0.002) and ultrasound features ( <0.001) were related to the initial treatment response. On multivariate analysis, sTg level ( =1.186, <0.001) and LNM size ( =1.533, =0.004) were independent risk factors for IR after initial I therapy. The optimal sTg level and LNM size cutoff value for predicting the treatment response after initial I therapy were 18.2 µg/l and 5mm. This study suggested that approximately one-quarter of patients with I+ lymph nodes on initial PTS, especially those with N0 or N1a stage, lower sTg level, smaller LNM size, ≤2 residual/recurrent LNMs, negative ultrasound features and no I- LNM, remain stable after one cycle of I therapy and do not need repeated therapy.