A PHASE-II STUDY OF TREATMENT OF PAINFUL MULTIFOCAL SKELETAL METASTASES WITH SINGLE AND REPEATED DOSE SM-153 ETHYLENEDIAMINETETRAMETHYLENE PHOSPHONATE

A phase II study of Sm-153 ethylenediaminetetramethylene phosphonate (Sm-153-EDTMP) palliative treatment was conducted on 23 patients with painful disseminated skeletal metastases. The administered activity of Sm-153-EDTMP was determined by prospective dosimetry and the radiation absorbed dose to bone marrow was fixed at 2 Gy. Symptomatic relief of bone pain was experienced by 14 of 23 evaluable patients (61%) with a median duration of 8 weeks (range 0-40). Toxicity was limited to myelosuppression with median nadir counts of leucocytes 3.3 x 10(9)/l (range 1.0-7.5) and platelets 133 x 10(9)/l (range 24-176) occurring at 2 weeks and 4 weeks, respectively. Retreatment with Sm-153-EDTMP was studied in 15 patients, including in 4 of the 23 patients treated with a single dose. The retreatment median radiation absorbed dose to red marrow was 1.9 Gy given at a median of 9 weeks (range 6-38) after initial treatment. Good control of pain was obtained in 13 of these patients (87%). Both the median duration of pain control (24 weeks) and survival (9 months) in the retreated group were substantially greater than for patients treated with a single dose, where duration was 8 weeks and survival 4 months. Additional toxicity in the retreated patients was confined to anaemia which required blood transfusion in 9 of the 15 patients (60%).