Department of Medical Physics and Radiation Protection, Gurutzeta-Cruces University Hospital/Biocruces Health Research Institute, Barakaldo, Spain; Faculty of Engineering, Department of Applied Physics I, UPV/EHU, Bilbao, Spain.
Department of Nuclear Medicine, Gurutzeta-Cruces University Hospital/Biocruces Health Research Institute, Barakaldo, Spain.
Phys Med. 2019 Sep;65:143-149. doi: 10.1016/j.ejmp.2019.08.017. Epub 2019 Aug 29.
To analyse the activity uptakes, effective half-lives and time-integrated activities, of relevance for remnant dosimetry, for patients treated for papillary thyroid cancer (PTC) with a different amount of activity of I-NaI.
Fifty patients were included. Of those, 18 patients had low-risk PTC and were treated with 1.11 GBq of I-NaI (Group 1), and 32 patients had high-risk PTC and were treated with 3.7 GBq (Group 2). Radioiodine was administered after total thyroidectomy and rhTSH stimulation. Two SPECT/CT scans were performed for each patient to determine the remnant activities and effective half-lives.
Significantly higher values (p < 0.05) were obtained for Group 1 for the remnant activity at 7 d (medians 1.4 MBq vs 0.27 MBq), the remnant activity per administered activity at 2 d (0.35% vs 0.09%) and at 7 d (0.13% vs 0.007%), and the effective half-life (93 h vs 40 h). Likewise, the time-integrated activity coefficient was significantly higher for Group 1. The time-integrated activity did not differ significantly between the two groups (p > 0.05).
We found a significant difference in the remnant activity per administered activity, the rate of washout from thyroid remnants, and the time-integrated activity coefficient between low-risk PTC patients treated with 1.11 GBq and high-risk PTC patients treated with 3.7 GBq. On the contrary, there was no such difference in the time-integrated activity. If remnant masses were also not statistically different (reasonable assumption for this monocentric study) no difference in time-integrated activity would imply no difference in remnant absorbed dose, of relevance for treatment efficacy and the risks of stochastic effects.
分析接受不同碘-123 活度治疗的甲状腺乳头状癌（PTC）患者的残留剂量相关的放射性活度摄取量、有效半衰期和时间积分活度。
纳入 50 例患者。其中，18 例低危 PTC 患者接受 1.11GBq 的碘-123 治疗（1 组），32 例高危 PTC 患者接受 3.7GBq 的碘-123 治疗（2 组）。所有患者均在甲状腺全切术后和 rhTSH 刺激后进行碘-123 治疗。每位患者均进行两次 SPECT/CT 扫描，以确定残留活性和有效半衰期。
1 组的残留活性在第 7 天（中位数分别为 1.4MBq 和 0.27MBq）、第 2 天（0.35%和 0.09%）和第 7 天（0.13%和 0.007%）及第 2 天（93h 和 40h）时的有效半衰期明显更高（p<0.05）。同样，1 组的时间积分活度系数也明显更高。两组间的总积分活度无明显差异（p>0.05）。
我们发现，接受 1.11GBq 碘-123 治疗的低危 PTC 患者和接受 3.7GBq 碘-123 治疗的高危 PTC 患者之间，残留活性与给予的活性之比、甲状腺残留组织清除率以及时间积分活度系数存在显著差异。相反，时间积分活度没有差异。如果残留组织的差异也没有统计学意义（基于该单中心研究的合理假设），那么时间积分活度的差异就意味着残留吸收剂量没有差异，这对治疗效果和随机效应风险有重要意义。
