Purpose: To date, the survival benefits of multiple radioactive iodine therapies (RAIT) in RAI-avid pulmonary micrometastatic differentiated thyroid cancer (DTC) remain debatable. This study aimed to compare the progression-free survival (PFS) benefits between those received only once RAIT (o-RAIT) and multiple RAITs (m-RAIT) in such patients.

Methods: Patients with RAI-avid pulmonary micrometastatic DTC were included and divided into either o-RAIT or m-RAIT group according to the number of RAIT cycles. The response to first RAIT in all patients and last RAIT in m-RAIT were evaluated and classified as partial response (PR), stable disease (SD), and progressive disease (PD). PFS was defined as the time from first RAIT to PD. Logistic regression analysis and Kaplan-Meier survival curves were employed to identify risk factors and estimate PFS, with propensity score matching (PSM) to reduce confounders.

Results: A total of 117 patients with RAI-avid pulmonary micrometastatic DTC were retrospectively included, with 38 (32.5%) from o-RAIT and 79 (67.5%) from m-RAIT. Patients from m-RAIT exhibited younger age at diagnosis, more local persistent disease before RAIT, and more metachronous metastasis compared with o-RAIT group (all P < 0.05). In the comparison of RAIT response, there was no difference in the first RAIT response between the o-RAIT and m-RAIT, while the last RAIT response of m-RAIT is worse not only than o-RAIT (P = 0.005), but also than their own first RAIT response (P = 0.0003). Multivariate analysis revealed age at diagnosis (over 45 years old) (P = 0.006) and local persistent disease before RAIT (P = 0.001) were independent risk factors for PD after RAIT, while number of RAIT cycles was not. To minimize potential confounders, the risk factors for PD and follow-up time were matched by PSM, after which, no significant difference in PFS was observed between the matched o-RAIT and m-RAIT (5-year PFS rate: 83.6% vs. 81.6%, P = 0.808).

Conclusions: In patients with RAI-avid pulmonary micrometastatic DTC, o-RAIT exhibited non-inferior PFS benefits compared with m-RAIT, suggesting the "less is more" management strategy of RAIT towards such patients.

Keywords: Differentiated thyroid cancer; Progression-free survival; Propensity score matching; Pulmonary micrometastasis; Radioactive iodine-avid lesion.

© 2025. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.

目的： 至今，多次放射性碘治疗（RAIT）对摄取放射性碘的肺微转移分化型甲状腺癌（DTC）患者的生存益处仍然存在争议。本研究旨在比较仅接受一次 RAIT （o-RAIT）和多次 RAITs （m-RAIT）患者在无进展生存期（PFS）方面的差异。

方法： 纳入有摄取放射性碘肺微转移 DTC 的患者，并根据 RAIT 周期数将其分为 o-RAIT 或 m-RAIT 组。对所有患者的首次 RAIT 和多次 RAIT 患者的最后一次 RAIT 进行评估并分类为部分缓解（PR）、疾病稳定（SD）和疾病进展（PD）。PFS 定义为从第一次 RAIT 至 PD 的时间。通过逻辑回归分析和 Kaplan-Meier 生存曲线来识别风险因素并估计 PFS，同时使用倾向评分匹配（PSM）以减少混杂因素。

结果： 共回顾性纳入 117 名有摄取放射性碘肺微转移 DTC 的患者，其中 38 名（32.5%）来自 o-RAIT 组，79 名（67.5%）来自 m-RAIT 组。m-RAIT 组的诊断年龄较年轻、更易在 RAIT 前有局部持续性病变及更多继发转移病灶与 o-RAIT 组相比均有显著差异 (所有 P

结论： 对于摄取放射性碘的肺微转移 DTC 患者，o-RAIT 的 PFS 益处并不劣于 m-RAIT，表明对这类患者采取“少即是多”的 RAIT 管理策略。

关键词： 分化型甲状腺癌；无进展生存期；倾向评分匹配；肺微转移；放射性碘摄取病灶。