Re-HEDP : pharmacokinetic characterization, clinical and dosimetric evaluation in osseous metastatic patients with two levels of radiopharmaceutical dose

Patients received 1.3 or 2.2 GBq, in single or multiple doses. Platelets, white and red cells were evaluated during 11 weeks. Pharmacokinetic characterization was done from blood and urine samples for 5 patients along 24 hours. Urinary excretion was evaluated in other 16 patients during 6 hours. Bone uptake was estimated as remaining activity in whole body. Scintigraphic images were acquired at 2 and 24 hs post-administration. Absorbed dose in bone marrow was estimated with Mirdose3. Analgesics intake and pain score were daily recorded. Tumour markers (PSA, and Tn-structure) were monitored in 9 patients during 4 to 6 months. Single doses of low activity (1.3 GBq) were given to twelve patients. Nine patients received multiple doses.All except one patient had normal levels of platelets, white and red cells. Remaining dose in blood at 2 hours was 9%. Urinary elimination was 58%. Bone uptake at 24 hours was 43% (mean value; n = 5). No changes of the haematological parameters were detected along follow-up period. Pain relief was evidenced by decrease or supression of opioid analgesic and by subjective index. PSA showed a decrease in prostate cancer patients (n = 4). Tn-structure showed a significant increase after 4 to 8 months.Single or multiple dose scheme could be safely used, with administered activity of 188Re-HEDP up to 60 mCi, with low bone marrow absorbed doses.Cancer is the second more frequent cause of death, after cardiovascular disease in developed countries. Most of adult patients with neoplasms will develop skeletal metastases that can lead to progressive pain. The development of less toxic but equally effective pain relieving agents for bone metastases has been a field of increasing interest to nuclear medicine [1-6]. In that sense, the application of bone-seeking radiopharmaceuticals is a promising alternative for hemi-body or whole-body radiotherapy.After the successful application of 32P and 89Sr [7-9], new β- emitter phosphonate radiopharmaceuticals we