2561 Effects of concomitant use of abiraterone and/or enzalutamide with radium-223 on safety and overall survival in metastatic castration-resistant prostate cancer (mCRPC) patients treated in an international early access program (EAP)

[Radium-223 dichloride in patients with castration-refractory prostate cancer]

Since November 2013, the alpha emitter radium-223 dichloride (Alpharadin/Xofigo®) has been approved for the treatment of men with castration-resistant prostate cancer (CRPC) with symptomatic bone metastases and no known visceral metastatic disease. In the ASYMPCA clinical trial, radium-223 was shown to improve overall survival and to reduce the time to the first symptomatic skeletal event. The use of radium-223 was associated with a reduction of pain and an improvement of health-related quality of life compared to the placebo arm. The efficacy of radium-223 dichloride was not inhibited by the use of chemotherapy with docetaxel. Studies have demonstrated a longer overall survival (OS) in patients with a combined treatment of abiraterone or enzalutamide; however, until this data is validated in larger clinical trials, the combination of radium-223 and abiraterone/enzalutamide cannot be recommended. Patients who have received concomitant medication with denosumab appeared to have a longer OS compared to patients who did not. A second treatment cycle of radium-223 was not associated with any adverse events when compared to the outcomes reported in the ASLYMPCA trial. Here the median radiographic progression-free survival was 9 months.

Efficacy and Safety of Radium-223 Dichloride in Symptomatic Castration-resistant Prostate Cancer Patients With or Without Baseline Opioid Use From the Phase 3 ALSYMPCA Trial

BACKGROUND

The phase 3 ALSYMPCA trial enrolled metastatic castration-resistant prostate cancer patients with or without baseline opioid use.

OBJECTIVE

To assess the efficacy and safety of radium-223 dichloride (radium-223) versus placebo in ALSYMPCA patients by baseline opioid use.

DESIGN, SETTING, AND PARTICIPANTS

Nine hundred and twenty one patients enrolled at 136 centers globally.

INTERVENTION

Radium-223 (50 kBq/kg, intravenous injection) every 4 wk for six cycles or matching placebo, each plus best standard of care.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Primary endpoint (overall survival [OS]), main secondary efficacy endpoints, and safety were evaluated by baseline opioid use. Additional analyses included time to first opioid use, time to first external beam radiation therapy for bone pain, and safety of concomitant external beam radiation therapy.

RESULTS AND LIMITATIONS

At baseline, 408 (44%) patients had no pain and no analgesic use or mild pain with nonopioid therapy (World Health Organization ladder pain score 0-1 [nonopioid subgroup]), and 513 (56%) had moderate pain with occasional opioids or severe pain with regular daily opioids (World Health Organization ladder pain score 2-3 [opioid subgroup]). Radium-223 significantly prolonged OS versus placebo in nonopioid (hazard ratio [HR]=0.70; 95% confidence interval [CI]: 0.52-0.93; p=0.013) and opioid (HR=0.68; 95% CI: 0.54-0.86; p=0.001) subgroups, and significantly reduced risk of symptomatic skeletal events versus placebo, regardless of baseline opioid use (nonopioid subgroup: HR=0.56, 95% CI: 0.39-0.82, p=0.002; opioid subgroup: HR=0.72, 95% CI: 0.53-0.98, p=0.038). Time to first opioid use for bone pain was significantly delayed with radium-223 versus placebo (HR=0.62, 95% CI: 0.46-0.85, p=0.002). Adverse event incidences were similar between opioid subgroups.

CONCLUSIONS

Radium-223 versus placebo significantly prolonged OS and reduced symptomatic skeletal event risk with a favorable safety profile in castration-resistant prostate cancer patients with symptomatic bone metastases, regardless of baseline opioid use.

PATIENT SUMMARY

In this ALSYMPCA opioid subgroup analysis, baseline symptom levels did not appear to impact radium-223 dichloride efficacy or safety.

Radionuclide Therapies in Prostate Cancer: Integrating Radium-223 in the Treatment of Patients With Metastatic Castration-Resistant Prostate Cancer

Metastatic castration-resistant prostate cancer (mCRPC) frequently metastasizes to the bone, often resulting in painful skeletal events, reduced quality of life, and reduced survival. The beta-emitting radiopharmaceuticals strontium-89 and samarium-153 alleviated pain in mCRPC patients with widespread skeletal metastases and have been associated with myelotoxicity. Radium-223, a first-in-class alpha-emitting radiopharmaceutical, prolonged overall survival, delayed symptomatic skeletal events, and improved quality of life, versus placebo, in patients with CRPC and symptomatic bone metastases and no visceral metastases. Radium-223 provided survival benefit to patients with CRPC and symptomatic bone metastases, regardless of prior docetaxel use. Importantly, prostate-specific antigen level and pain palliation were not a measure of radium-223 treatment response and should not alter the decision to administer all six radium-223 injections, the recommended regimen for survival benefit. Radium-223 was generally well tolerated, leading to ongoing clinical trials in combination with other therapeutics. Thus, radium-223 is a valuable addition to the mCRPC treatment armamentarium.