Rhenium-188-HEDP in the palliative treatment of bone metastases

Rhenium-188-HEDP (188Re-HEDP) is a new and attractive radiopharmaceutical for the treatment of bone pain due to metastases. As a product of a 188W/188Re generator it is convenient for clinical use. With a short physical half life of 16.9 hours and a maximal beta-energy of 2.1 MeV, it is suitable for therapy.

We investigated the influence of 188Re-HEDP on pain relief, analgesic intake and impairment of bone marrow function in 15 patients. All patients were interviewed using standardized questions before, and 1, 2, 3, 4, 8, and 12 weeks after therapy. Blood samples were drawn weekly for 12 weeks, and a blood count was performed. Patients underwent gamma camera imaging to determine the radionuclide accumulation 4, 20, and 28 hours after therapy. The patients were treated with 1600 to 3459 MBq of 188Re-HEDP.

Patients showed an improvement of the Karnofsky performance index from 74 +/- 8% to 84 +/- 11% 12 weeks after therapy. This improvement was statistically significant (p = 0.001). Eighty percent of the patients described pain relief and reduction of analgesics. Twenty percent of the patients could discontinue their analgesics. Mean platelet count decreased from (284 +/- 84)*10(3)/microliter to (205 +/- 62)*10(3)/microliter, and mean leukocyte count from (7.5 +/- 1.5)*10(3)/microliter to (5.9 +/- 2.1)*10(3)/microliter after therapy. The maximal differences between the values of platelets and leukocytes before and after therapy were not statistically significant (p = 0.021 and p = 0.094). Prostate specific antigen decreased from 95 +/- 83 ng/ml to 41 +/- 21 ng/ml, the difference was not statistically significant (p = 0.443). The bone accumulation 4, 20, and 28 hours after therapy was 1.3 +/- 0.5%, 0.6 +/- 0.3%, and 0.45 +/- 0.2% of the injected dose of a single metastasis, and 57 +/- 17%, 15.5 +/- 2% and 11 +/- 3% in the whole body, respectively. The effective half-life of 188Re-HEDP was 15.3 +/- 3.0 hours in the bone metastases, and 11.4 +/- 2.8 hours in the whole body. This corresponds to a residence time of 0.22 +/- 0.25 hours in the bone metastases, and of 10.54 +/- 2.59 hours in the whole body.

In a small patient population, 188Re-HEDP therapy for bone pain palliation was effective and was associated with minimal toxicity.