Impact of treatment delay in Radium-223 therapy of metastatic castration-resistant prostate cancer patients

Radium-223-dichloride (Ra-223) is an alpha-emitting, bone seeking radionuclide therapy approved for patients with metastatic castration-resistant prostate cancer (mCRPC). In the fall of 2014, a global temporary shortage of Ra-223 occurred for 2 months due to production irregularities. The aim of this study was to assess whether prolonged interval between Ra-223 cycles to non-disease related causes had a negative impact on clinical outcome of therapy. Retrospective single-center study of mCRPC patients who initiated Ra-223 therapy in the period from March 2014 to February 2015. End points were number of completed Ra-223 cycles, overall survival (OS) and radiographic progression-free survival (rPFS). Bone scintigraphy, CT of thorax and abdomen, hematological status, PSA and alkaline phosphatase were evaluated prior to first dose and after 3rd and 6th treatment, respectively. Follow-up period was 18 months after first Ra-223 cycle. A total of 50 consecutive patients initiated Ra-223 therapy in the time period. Seventeen of 50 patients (34%) had prolonged interval between cycles due to delivery problems. Median delay was 4 weeks (range 3-9 weeks). Patients with delayed treatment had significantly longer median rPFS [delayed patients: 7.1 months (95% CI 4.9-9.3) vs. 4.5 months (95% CI 2.8-6.3)]. There was no significant difference in number of completed cycles or median OS. We find no negative impact of prolonged interval between Ra-223 cycles due to non-disease related reasons on OS, rPFS or number of completed treatment cycles.