Re-186-etidronate in breast cancer patients with metastatic bone pain

The aim of this study was to evaluate the efficacy of (186)-Re-1,1 -hydroxy ethylidene diphosphonate (etidronate) in breast cancer patients with painfu l bone metastases. Methods: Thirty patients with advanced breast cancer who had metastatic bone pain were treated with Re-186-etidronate using differe nt dosages in a noncomparative, open-label study. Twenty-four patients were evaluated for efficacy (6 patients had incomplete datasets), Dosages varie d from 1295 to 2960 MBq (35 to 80 mCi). Efficacy was evaluated according to the multidimensional pain model using a paper-and-pencil diary. The diary was kept twice daily for 8-10 wk (2 wk before through 6-8 wk after Re-186-e tidronate treatment). Response was determined with a strict criteria, in wh ich pain intensity (PI), medication index (MI) and daily activities (DA) we re core determinants. Response was defined as: (a) Reduced PI greater than or equal to 5% while MI and DA were at least constant; or (b) Reduced PI <2 5% in combination with improvement of MI or DA greater than or equal to 25% , without worsening of either factor. Duration of response should always ex ceed a minimum of 2 wk. Results: Fifty-eight percent (n = 14) of all patien ts reported a response. The maximum follow-up period was 8 wk. Duration of response ranged from 2 to 8 wk (mean 4 wk). Patients (14/24) not only exper ienced considerable pain reduction, but in 12 patients this was also accomp anied by noteworthy reduction in Mi (greater than or equal to 25%). No clea r dose-response relationship was found. Conclusion: With strict pain assess ment criteria, 186Re-etidronate showed a response of 58% in the palliative treatment of metastatic bone pain originating from breast cancer.