Use of radium-223 in heavily pretreated metastatic castrate resistant prostate cancer (mCRPC) patients.

Abstract

275 Background: Ra 223 has been shown to improve overall survival in mCRPC patients with symptomatic bone metastases. Little is known about the utility of following PSA during Ra 223 therapy in heavily pretreated patients. Here we report our experience with Ra 223 in such a setting. Methods: We reviewed 26 heavily pretreated mCRPC patients who received Ra 223 at 3 institutions and evaluated the trend of PSA during treatment, the association of various demographic, clinical and biochemical variables with PSA trend, and the correlation of PSA trend with clinical outcomes. Patients received IV Ra 223 every 4 weeks with a planned total of 6 cycles. Results: Twenty six patients were treated between August 2013 and August 2014. Median age was 70 years (range 49-80); 77% (N=20) were European American (EA), 19% (N=5) were African Americans (AA), unknown for 1 patient. Prior therapy included docetaxel in 77% (N=20) of patients, cabazitaxel in 19% (N=5), enzalutamide in 65% (N=17), and abiraterone in 54% (N=14). 62% (N=16) received at least 3 prior therapies.35% (N=9) received all 6 cycles of Ra 223, while 18% (N=4) received only 1 cycle. Median alkaline phosphatase level increased from 126.0 U/L (54.0, 514.0) to 332.0 U/L (136.0, 566.0) at the end of Ra 223 therapy. Median pre-therapy PSA was 100.3 and median post-therapy PSA was 429.5. 54% (N=14) patients had >50% rise in PSA. Higher pre-therapy PSA was strongly associated with higher post-therapy PSA (Pearson’s correlation coefficient = 0.84, p <0.0001). Faster rate of rise in PSA was observed in patients with higher number of bone metastasis and those who have had prior therapy with docetaxel. The patients with >50% PSA rise had reported overall higher pain scores by visual assessment scale. Ra 223 was discontinued in 15% (N=4) patients due to myelosuppression and in 8% (N=2) due to side effects. Conclusions: All heavily pretreated patients receiving Ra 223 therapy for mCRPC showed PSA progression and reasonable tolerability. Only 35% of patients were able to receive all 6 cycles of Ra 223.