Department of Radiology, Oncology and Radiation Science, Section of Nuclear Medicine, Uppsala University Hospital, Sweden.
Acta Oncol. 2012 Jan;51(1):86-96. doi: 10.3109/0284186X.2011.618511. Epub 2011 Oct 3.
Fractionated (177)Lu-DOTA-octreotate therapy has been reported to be an effective treatment option for patients with generalized neuroendocrine tumors. In our clinic, full individual dosimetry is performed during the first therapy cycle, while dosimetry at later cycles is based on the 24 h uptake measurement assuming an unchanged effective half-life. Our aim was to evaluate this assumption and the variation in the 24 h uptake during therapy.
Thirty patients, 13 women and 17 men, were included in the study.
During the first therapy cycle the (177)Lu-concentration was measured with SPECT/CT over the abdomen at 24 h, 96 h and 168 h after infusion. The effective half-life was determined for the kidneys, liver and spleen. The procedure was repeated at cycle 4 or 5.
The median ratio between the effective half-lives of the latter and the first cycle was 0.97 and 1.01 for the right and left kidney, with a range of 0.89-1.01 (1st-3rd quartile) and 0.93-1.05, respectively.
The mean value of the ratios was slightly lower than one, indicating a tendency towards increased activity elimination during therapy. In individual patients, significant changes were found for all organs, often when a large tumor burden reduction occurred during treatment. Possible contributing factors appeared to be larger amounts of non-tumor bound tracer, improved organ function (kidneys), decrease of vessel obstruction (spleen), less scatter from large tumors and reduction of small metastases (liver and spleen).
With most patients it is safe to estimate absorbed doses to kidneys, liver and spleen from 24 h activity concentration assuming an unchanged effective half-life during therapy. Patients with risk factors for kidney dysfunction need to be monitored in more detail. Simplified dosimetry based on the assumption of unchanged effective half-life can function as guidance to the number of therapy cycles an individual patient can tolerate.
已报道分次（177）Lu-DOTA-奥曲肽治疗对广泛神经内分泌肿瘤患者是一种有效的治疗选择。在我们的诊所，在第一个治疗周期期间进行全身个体剂量测定，而在以后的周期中，根据 24 小时摄取量测量值假设有效半衰期不变来进行剂量测定。我们的目的是评估这种假设以及治疗期间 24 小时摄取量的变化。
本研究纳入了 30 名患者，包括 13 名女性和 17 名男性。在第一个治疗周期中，在输注后 24、96 和 168 小时，使用 SPECT/CT 对腹部进行（177）Lu 浓度测量。确定了肾脏、肝脏和脾脏的有效半衰期。该程序在第 4 或第 5 个周期重复进行。
后一周期和第一个周期的有效半衰期之间的中位数比值分别为右肾和左肾的 0.97 和 1.01，范围分别为 0.89-1.01（1 至 3 四分位数）和 0.93-1.05。
比值的平均值略低于 1，表明在治疗过程中活性清除率有增加的趋势。在个别患者中，所有器官都发现了显著变化，通常在治疗过程中肿瘤负荷大量减少时。可能的促成因素似乎是未结合示踪剂的量增加、器官功能改善（肾脏）、血管阻塞减少（脾脏）、来自大肿瘤的散射减少以及小转移灶减少（肝脏和脾脏）。
对于大多数患者，可以安全地假设在治疗期间有效半衰期不变，从 24 小时活性浓度估算肾脏、肝脏和脾脏的吸收剂量。需要更详细地监测有肾功能障碍风险的患者。基于有效半衰期不变的假设简化剂量测定可作为指导个体患者可耐受的治疗周期数的依据。
