Radium-223 in Heavily Pretreated Metastatic Castrate-Resistant Prostate Cancer.

Background: Radium-223 is a bone-targeting radiopharmaceutical that extends survival in mCRPC. Postapproval data are limited, and the value of biochemical and radiologic monitoring during radium therapy is unknown.
Patients and Methods: We conducted a retrospective study of 29 patients with mCRPC who received radium-223 at 1 of 3 participating institutions between August 2013 and December 2014. Trend of PSA, radiographic changes, and association of biochemical and clinical variables with PSA trend were measured.
Results: The median age of patients was 70 years, 79% of patients (N = 23) were European Americans, and 17% of patients (N = 5) were African Americans. Twenty patients (69%) had received at least 3 lines of prior therapies. Some 38% of patients (N = 11) received all 6 cycles of radium-223. Twenty patients (69%) had an increase in PSA during radium therapy, and 4 patients (14%) had a decline in PSA levels. Five patients had visceral metastases on computed tomography imaging performed during the course of radium-223.
Conclusions: Radium therapy in mCRPC was associated with an increase in PSA in the majority of these heavily pretreated patients. The development of visceral disease was not uncommon, suggesting a need for follow-up computed tomography monitoring during radium-223 therapy. The significance of early increases in PSA and pain with radium-223 is still uncertain. Although pain and PSA flare have been reported in patients who subsequently have a dramatic response to therapy, we observed that a PSA increase or pain flare correlates to an improvement in bone scans only in a minority of patients.
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