Study on the skeletal retention and bone marrow dose of Lu-177-EDTMP in patients with bone metastasis

Objectives 177Lu-EDTMP, as a new therapeutical agent of bone metastasis is now in a phase II clinical trial coducted by IAEA. This investigation sought to find out the correlation of Lu-177-EDTMP skeletal uptake and the extent of bone metastasis lesions according to the phase II data.

Methods 13 patients suffering with bone matastasis from prostate or breast cancer were included in this study. All the patients were given 177Lu-EDTMP for palliation of metastatic pain. Bone lesion score was used to estimate the extent of bone metastasis. The bone lesion score was given according to the amount of bone lesions of patients' 99mTc-MDP bone scan image. A simplified algorithm based on MIRDose algorithm was employed to calculate the uptake ratio of 177Lu-EDTMP in skeleton and the bone marrow dose according to the whole body images at 1hr and 24hr phases.

Results The bone lesion score (x) ranged from 8 to 19 (14.1 ± 4.1). The skeletal uptake ratio of 177Lu-EDTMP(y1) ranged from 28%~76% (52.7% ± 16.6%) of injected dose. Bone marrow dose of 177Lu-EDTMP (y2) was 0.12 ± 0.04 cGy/MBq. Linear regression analysis showed good correlation between skeletal uptake ratio and bone lesion score (y1 = 0.032x + 0.066, R=0.81) as well as that between bone marrow dose and bone lesion score (y2 = 0.008x + 0.009, R=0.80).

Conclusions The results can be illustrated that more metastasis lesions, higher skeletal uptake of 177Lu-EDTMP. 177Lu-EDTMP has fine affinity and retention in metastatic bone lesions. And the radiation effect is mainly on bone lesions.

Research Support IAEA CRP E1.30.3