Peptide receptor radionuclide therapy with 177Lu-DOTATATE is a recognized option for treating neuroendocrine tumors and has few toxicities, except for the kidneys and bone marrow. The bone marrow dose is generally derived from a SPECT/CT image-based method with four timepoints or from a blood-based method with up to 9 timepoints, but there is still no reference method. This retrospective single-center study on the same cohort of patients compared the calculated bone marrow dose administered with both methods using mono, bi- or tri-exponential models. For the image-based method, the dose was estimated using Planetdose© software. Pearson correlation coefficients were calculated. We also studied the impact of late timepoints for both methods. The bone marrow dose was calculated for 131 treatments with the blood-based method and for 17 with the image-based method. In the former, the median absorbed dose was 15.3, 20.5 and 28.3 mGy/GBq with the mono-, bi- and tri-exponential model, respectively. With the image-based method, the median absorbed dose was 63.9, 41.9 and 60.8 with the mono-, bi- and tri-exponential model, respectively. Blood samples after 24h post-injection did not evidence any change in the absorbed bone marrow dose with the bi-exponential model. On the contrary, the 6-day post-injection timepoint was more informative with the image-based model. This study confirms that the estimated bone marrow dose is significantly lower with the blood-based method than with the image-based method. The blood-based method with a bi-exponential model proved particularly useful, without the need for blood samples after 24h post-injection. Nevertheless, this blood-based method is based on an assumption that needs to be more validated. The important difference between the two methods does not allow to determine the optimal one to estimate the true absorbed dose and further studies are necessary to compare with biological effects.

中文翻译：

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基于血液样本和图像的不同模型对 177Lu 标记的生长抑素受体治疗后骨髓剂量测定的影响


使用 177Lu-DOTATATE 进行肽受体放射性核素治疗是治疗神经内分泌肿瘤的公认选择，并且除肾脏和骨髓外几乎没有毒性。骨髓剂量通常源自具有四个时间点的基于 SPECT/CT 图像的方法或具有最多 9 个时间点的基于血液的方法，但仍然没有参考方法。这项针对同一组患者的回顾性单中心研究使用单指数、双指数或三指数模型比较了两种方法所计算的骨髓剂量。对于基于图像的方法，使用 Planetdose© 软件估算剂量。计算皮尔逊相关系数。我们还研究了两种方法的延迟时间点的影响。使用基于血液的方法计算了 131 次治疗的骨髓剂量，使用基于图像的方法计算了 17 次治疗的骨髓剂量。前者的单指数、双指数和三指数模型的中位吸收剂量分别为 15.3、20.5 和 28.3 mGy/GBq。基于图像的方法，单指数、双指数和三指数模型的中位吸收剂量分别为 63.9、41.9 和 60.8。注射后 24 小时后的血样没有表明双指数模型吸收的骨髓剂量有任何变化。相反，基于图像的模型在注射后 6 天的时间点提供了更多信息。这项研究证实，基于血液的方法估计的骨髓剂量明显低于基于图像的方法。事实证明，采用双指数模型的基于血液的方法特别有用，无需在注射后 24 小时后采集血液样本。然而，这种基于血液的方法所基于的假设需要进一步验证。 两种方法之间的重要区别不允许确定估计真实吸收剂量的最佳方法，因此需要进一步研究以与生物效应进行比较。