Prospective dosimetry with 99mTc-MDP in metabolic radiotherapy of bone metastases with 153Sm-EDTMP

L. Bianchi, A. Baroli, L. Marzoli, C. Verusio, C. Chiesa, L. Pozzi

Research output: Contribution to journalArticle

Abstract

Purpose: On the basis of the encouraging results achieved in several clinical trials and its proven therapeutic efficacy, 153Sm-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 153Sm-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. Methods: Seven to 14 days before treatment with 153Sm-EDTMP, 44 patients underwent 99mTc-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. Results: 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. Conclusions: The rate of retention of 99mTc-MDP in bone provides a reliable estimate of the 153Sm-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 153Sm-EDTMP activity.

Original languageEnglish
Pages (from-to)122-129
Number of pages8
JournalEuropean Journal of Nuclear Medicine and Molecular Imaging
Volume36
Issue number1
DOIs
Publication statusPublished - Jan 2009

Keywords

  • Sm-EDTMP
  • Tc-MDP
  • Bone metastases
  • Internal dosimetry
  • Radionuclide therapy

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging

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