Clinical response to radium-223 dichloride in men with metastatic castrate-resistant prostate cancer

Factors Influencing Outcome Post–Radium-223 Dichloride in Castrate Resistant Prostate Cancer: A Review of Some Real-World Challenges

Aim Radium-223 has been the first-approved targeted Alpha therapy agent. We retrospectively assessed different factors influencing the overall survival (OS) and patient management.

Setting and Design Thirty-two metastatic castration-resistant prostate cancer (mCRPC) patients' hematological parameters, number of cycles, performance status, and toxicities were evaluated for OS. Radium 223 dichloride (Radium-223) was administered every 4 weeks for a maximum of six cycles. Primary and secondary end points were OS, progression free survival (PFS), therapy toxicities, change in performance status, biochemical response, and skeletal-related events (SREs).

Materials and Methods Patients' median age was 77 years (range: 57–90 years) and median follow-up was 399 days (range: 5–1,761 days). A total of 163 cycles were administered in 32 patients, with 4 or less cycles in 8 patients (25%) and 5 or more cycles in 24 patients (75%). Among eight patients with 4 or less cycles, three patients died, of which two patients died due to neutropenic sepsis.

Statistical Analysis Mann–Whitney test was used to compare the cycle groups; Spearman's correlation coefficient was used to see the relation of different variables with OS. Log rank test was used for group comparison while Kaplan–Meier survivorship was used for OS.

Results Statistical correlation was seen between the number of cycles (p=0.037) and hemoglobin (p=0.028). Kaplan–Meier OS (p=0.038) was correlated with the number of cycles (≤ 4 cycles and ≥ 5 cycles). OS was 173 days in patients with one to four cycles, 226 days in five cycles, and 493 days in six cycles. Myelosuppression leading to stopping of full six cycles was seen in 7 of 32 patients (22%) and significantly correlated to inferior OS (p=0.048).

Conclusion Higher number of Radium-223 cycles was seen to be associated with better OS. Prior myelosuppression was associated with poor OS. Patients with better hematological profile were more likely to complete the maximum number of the cycles with a better OS.

Safety and activity of radium-223 in metastatic castration-resistant prostate cancer: the experience of Istituto Nazionale dei Tumori

INTRODUCTION

Therapeutic decision-making in metastatic castration-resistant prostate cancer (mCRPC) represents an open challenge. Radium-223 is approved for patients with symptomatic bone metastases, no visceral involvement, progressing after at least 2 lines of systemic therapy, or ineligible for any other systemic treatment.

METHODS

We performed a retrospective, observational study on patients with mCRPC treated with radium-223 at our institution outside of clinical trials, to assess the safety and activity in a real-world population. Data regarding baseline patient/disease characteristics and treatment outcomes (number of cycles, treatment-related adverse events [AEs], cause of discontinuation, and best response) were collected.

RESULTS

Overall, 41 patients were treated from September 2015 to September 2018. Median age was 73 years; baseline Eastern Cooperative Oncology Group Performance Status (ECOG PS) was 0, 1, or 2 in 15%, 80%, and 5% of cases, respectively; and 3%, 41%, 44%, and 12% of patients had <6, 6-20, >20, and superscan bone lesions, respectively. A median number of 5 cycles (interquartile range 3-6) with median dose 19.52 MBq (interquartile range 12.87-24.83) was received. Treatment schedule was completed in 49% of cases; discontinuations due to AEs, disease-related death, or disease progression occurred in 24%, 33%, and 43% of patients, respectively. Any-grade AEs occurred in 73% and grade 3/4 treatment-related AEs occurred in 29% of patients, mainly anemia, decreased platelet count, and fatigue. No skeletal-related events or treatment-related deaths were recorded. After treatment, 66%, 2%, and 32% of patients had a stable, improved, or deteriorated ECOG PS versus baseline, respectively, and 24%, 61%, and 15% reported a stable, improved, or worsened pain symptom control. Post-treatment versus baseline alkaline phosphatase was reduced or stable in 46% and increased in 54% of patients, whereas prostate-specific antigen was decreased or stable in 83% and increased in 17% of patients.

CONCLUSIONS

Our study provides clinically useful real-world data on radium-223, highlighting the importance of multidisciplinary patient management to guarantee the best continuum of care for patients with mCRPC.