Department of Diagnostic Imaging and Nuclear Medicine, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjuku-ku, Tokyo, 162-8666, Japan.
Departments of Surgery II, Tokyo Women's Medical University, Tokyo, Japan.
Ann Nucl Med. 2020 Feb;34(2):144-151. doi: 10.1007/s12149-019-01432-y. Epub 2019 Dec 13.
The efficacy of low-dose radioiodine therapy (RIT) for intermediate-risk or high-risk differentiated thyroid cancer (DTC) patients is controversial. Because of the country's shortage of medical facilities for RIT, 1110-MBq RIT for higher risk DTC patients has been performed on an outpatient basis since 2010 in Japan. Herein, we addressed this issue and attempted to determine prognostic factors for the prediction of RIT outcomes.
We retrospectively analyzed the cases of 119 patients with papillary thyroid cancer who underwent their first RIT with 1110 MBq radioactive iodine (RAI) following a total thyroidectomy, including 65 (54.6%) intermediate-risk and 54 (45.4%) high-risk patients (according to Japan's 2018 clinical practical guidelines for thyroid tumors). Successful ablation was defined when a negative I-131 whole-body scan and thyroglobulin (Tg) < 2 ng/mL were obtained at a diagnostic scan performed 148-560 days (median 261 days) after the first RIT.
The overall ablation success rate was 23.4%. Although the ablation success rates of each pretreatment protocol [recombinant human thyroid stimulating hormone and thyroid hormone withdrawal (THW)] did not differ significantly, THW tended to result in a higher success rate than rhTSH. The Tg level at RIT was the only independent powerful predictive factor for successful ablation. The best cut-off value of Tg for predicting unsuccessful ablation was 9 ng/mL.
The ablation success rate was much lower than those of earlier studies; the most plausible reason would be that higher risk DTC patients were included in this study. The low-dose RIT routinely performed in Japan might be inadequate for the achievement of successful ablation. At least for patients with Tg > 9 ng/mL at the first RIT, a higher dose of RAI is recommended.
低剂量放射性碘治疗（RIT）在中危或高危分化型甲状腺癌（DTC）患者中的疗效存在争议。由于我国 RIT 医疗设施短缺，自 2010 年以来，日本一直对高危 DTC 患者进行 1110-MBq 的门诊 RIT。在此，我们解决了这个问题，并试图确定预测 RIT 结果的预后因素。
我们回顾性分析了 119 例接受全甲状腺切除术后首次 1110-MBq 放射性碘（RAI）RIT 的甲状腺乳头状癌患者的病例，其中 65 例（54.6%）为中危患者，54 例（45.4%）为高危患者（根据日本 2018 年甲状腺肿瘤临床实践指南）。首次 RIT 后 148-560 天（中位数 261 天）进行诊断性扫描时，获得阴性 I-131 全身扫描和甲状腺球蛋白（Tg）<2ng/mL 时，定义为消融成功。
总的消融成功率为 23.4%。虽然每种预处理方案（重组人促甲状腺激素和甲状腺激素停药（THW））的消融成功率没有显著差异，但 THW 倾向于比 rhTSH 产生更高的成功率。RIT 时的 Tg 水平是成功消融的唯一独立有力预测因素。预测消融失败的最佳 Tg 截断值为 9ng/mL。
消融成功率远低于早期研究；最合理的原因是本研究纳入了更多高危 DTC 患者。日本常规进行的低剂量 RIT 可能不足以实现成功消融。至少对于首次 RIT 时 Tg>9ng/mL 的患者，建议使用更高剂量的 RAI。
