Abstract
Abstract only 249 Background: Radium 223 is approved for use in patients with symptomatic bone metastasis from castrate resistant prostate cancer, and no known visceral metastatic disease. It is currently dosed in a weight based fashion, however it is only active in the skeleton, and it is distributed primarily to the bone. A more rational dosing regimen may be based off a patient’s height, and the highest safe dose has yet to be determined. Our study looks at the safety profile of radium 223 in the context of a height based dosing regimen. Methods: This is a retrospective, observational study of all patients receiving radium 223 at the Urology Cancer Center. The patients were dosed at 50 kilobecquerels per kilogram as prescribed in the product insert. The dose each patient received was then recalculated based upon the patient’s height. The medical record was then examined for side effects. Results: As of September 2013 total of 30 discreet patients have received a total of 58 doses at our site since radium 223 was approved. The lowest dose received based on height was 17.39 kBq/cm and the highest dose was 40.7 kBq/cm with an average dose of 27.4 kBq/cm. There were eight grade 1 toxicities. The side effect profile did not show any trends across the different levels of dosing regarding the number or grade of toxicity with a greater number occurring below the median dose. Six of the eight men with significant GI distress have had prior radiation. Conclusions: A height based dosing regimen may be more appropriate for a drug designed to treat only the skeleton. In our population, we administered a wide variety of doses when administered by height. Higher doses appear to be well tolerated, and the optimal dose has yet to be determined. We propose future studies with height-based dosing escalation to look at the safety and efficacy.