Bianchi L, Baroli A, Marzoli L, Verusio C, Chiesa C, Pozzi L
Struttura Complessa di Fisica Sanitaria, Azienda Ospedaliera Ospedale di Circolo di Busto Arsizio, p.le G.Solaro 3, 21052, Busto Arsizio, Varese, Italy.
Eur J Nucl Med Mol Imaging. 2009 Jan;36(1):122-9. doi: 10.1007/s00259-008-0926-7. Epub 2008 Aug 28.
On the basis of the encouraging results achieved in several clinical trials and its proven therapeutic efficacy, (153)Sm-ethylene diamine tetramethylene phosphonic acid (EDTMP) has become widely used to palliate pain from bone metastases. The results reported in the literature have led the product suppliers (QUADRAMET, Schering) to suggest administering a fixed activity per kilogram (37 MBq/kg). However, considering the observed extreme inter-patient variability of skeletal uptake of (153)Sm-EDTMP, a real therapy optimization would require the individualization of the activity to be administered on a dosimetric basis. This should be planned taking into account the generally accepted 2-Gy dose constraint to the haematopoietic red marrow, the critical organ in palliative treatments with beta-emitting, bone-seeking radiopharmaceuticals.
Seven to 14 days before treatment with (153)Sm-EDTMP, 44 patients underwent (99m)Tc-methylene diphosphonate (MDP) total-body bone scan with two scans (the first within 10 min of injection, the second after 6 h). The percentage bone uptake (Tc(%)) was evaluated as the ratio between total counts at 6 h, adjusted for decay, and total counts at the first scan. Tc(%) was then compared to Sm(%) similarly derived from 10-min and 24-h whole-body scans. Tc(%) and Sm(%) were compared both with and without Brenner's method for soft tissue uptake.
The correlation between Tc(%) and Sm(%) was R (2) = 0.81 and R (2) = 0.88 with and without soft tissue correction, respectively. The difference between their average values was statistically significant (Sm(%) = 64.3 +/- 15.2, Tc(%) = 56.2 +/- 16.0; p = 0.017) with soft tissue correction, while was not statistically significant (Sm(%) = 68.2 +/- 15.5, Tc(%) = 66.9 +/- 14.0; p = 0.670) without soft tissue correction.
The rate of retention of (99m)Tc-MDP in bone provides a reliable estimate of the (153)Sm-EDTMP rate of retention. The proposed method can be usefully adopted for prospective dosimetry seeing its extreme simplicity, and it requires no special investment in terms of human or instrumental resources. This allows an optimization of administered (153)Sm-EDTMP activity.
基于多项临床试验取得的令人鼓舞的结果及其已证实的治疗效果，（153）钐 - 乙二胺四亚甲基膦酸（EDTMP）已被广泛用于缓解骨转移疼痛。文献报道的结果促使产品供应商（QUADRAMET，先灵公司）建议按每千克固定活度（37 MBq/kg）给药。然而，考虑到观察到的（153）Sm - EDTMP骨骼摄取在患者间存在极大差异，真正的治疗优化需要基于剂量学个体化给药活度。这一规划应考虑到在使用发射β射线、亲骨性放射性药物进行姑息治疗时，公认的对造血红骨髓的2 - Gy剂量限制，造血红骨髓是关键器官。
在使用（153）Sm - EDTMP治疗前7至14天，44例患者接受了（99m）锝 - 亚甲基二膦酸盐（MDP）全身骨扫描，进行两次扫描（第一次在注射后10分钟内，第二次在6小时后）。骨摄取百分比（Tc(%)）评估为6小时经衰变校正后的总计数与第一次扫描总计数之比。然后将Tc(%)与同样从10分钟和24小时全身扫描得出的Sm(%)进行比较。分别在考虑和不考虑布伦纳软组织摄取校正方法的情况下比较Tc(%)和Sm(%)。
在考虑和不考虑软组织校正的情况下，Tc(%)与Sm(%)的相关性分别为R² = 0.81和R² = 0.88。在考虑软组织校正时，它们平均值之间的差异具有统计学意义（Sm(%) = 64.3 ± 15.2，Tc(%) = 56.2 ± 16.0；p = 0.017），而在不考虑软组织校正时差异无统计学意义（Sm(%) = 68.2 ± 15.5，Tc(%) = 66.9 ± 14.0；p = 0.670）。
（99m）Tc - MDP在骨中的滞留率可对（153）Sm - EDTMP的滞留率提供可靠估计。所提出的方法因其极其简单，且在人力或仪器资源方面无需特殊投入，可有效地用于前瞻性剂量测定。这有助于优化（153）Sm - EDTMP的给药活度。
