Table 3 Summary of clinical trials evaluating radiopharmaceuticals. Radionuclides are typically administered in an outpatient setting through intravenous (IV) access. Authorized administers inject the radiopharmaceutical over the course of approximately 1 to 2 minutes followed by a saline flush. After the IV has been removed, patients are provided Enzalutamide order with instructions for increased fluid intake and urinary excretion. Weekly blood counts are obtained to assess any change secondary to the therapy administered. Phosphorous-32 (32P) was the first radionuclide to be consistently used in bone metastases and is available in an oral form, which allows for decreased cost and increased convenience. However, this radiotracer has fallen out of favor due to the high rates of myelotoxicity secondary to its longer range in targeted tissue and high energy decay [24�C26, 28].

Strontium-89 (89Sr) is administered as an IV injection and is beta emitter with a half-life of 50.5 days. Because of chemical similarities with calcium, 89Sr is rapidly taken up in bony matrix, especially where active bone formation exists. 89Sr was one of the first radiopharmaceuticals approved for the treatment of widespread bone metastases; thus there is abundant data reporting on outcomes and pain response to this therapy. Overall pain response to 89Sr is approximately 60% to 90%, especially in patients with metastatic breast and prostate cancer [25, 36�C38]. 89Sr use has been studied alone and in conjunction with radiation and chemotherapy.

Porter and McEwan prospectively evaluated 126 patients with hormone refractory prostate cancer that were randomized to radiation therapy followed by a single injection of 89Sr or radiation followed by placebo. Overall response rates were not significantly different in the two arms; however there was a decrease of the requirement for analgesics (2.4% versus 17.1%, P < 0.05) in favor of the combined modality group [31]. Samarium-152 ethylenediaminetetramethylenephosphonate (EDTMP) (153Sm-EDTMP) is a bone-seeking radioisotope with a short half-life of 46.3 hours that is slowly administered through IV injection. 153Sm is chelated to EDTMP to allow for delivery in areas of high bone turnover in patients with metastatic disease. Clinical response and experience with 153Sm is somewhat limited, but published reports have indicated pain response rates of approximately 70 to 80% [25, 26, 33�C35].

Collins et al. evaluated 20 patients with escalated dose regimens of 1.0, 1.5, 2.0, 2.5, and 3.0miCi/kg 153Sm EDTMP. The maximum tolerated dose was found to be 2.5mCi/kg Brefeldin_A in this patient population. Overall pain relief occurred in 76% of patients within 1 to 2 weeks of administration [34]. Radium-223 (223Ra) is a radiopharmaceutical alpha-emitter with a half-life of 11.4 days that acts as a calcium analogue. 223Ra was recently approved in the use of hormone refractory metastatic prostate cancer [28].