Radium‐223 dichloride treatment in metastatic castration‐resistant prostate cancer in Finland: A real‐world evidence multicenter study

BACKGROUND: Radium‐233 dichloride is an alpha emitter that specifically targets bone metastases in prostate cancer. Results of a previously reported phase III randomized trial showed survival benefit for radium‐223 compared to best supportive care in castration‐resistant prostate cancer (CRPC) with bone metastases. However, real‐world data are also needed with wider inclusion criteria. METHODS: We report results of a retrospective multicenter study including all patients with metastatic CRPC treated with radium‐223 in all five university hospitals in Finland since the introduction of the treatment. We identified 160 patients who had received radium‐223 in Finland in 2014–2019. RESULTS: The median overall survival (OS) was 13.8 months (range 0.5–57 months), and the median real‐world progression‐free survival (rwPFS) was 4.9 months (range 0.5–29.8 months). Alkaline phosphatase (ALP) values within the normal range before and during the radium‐223 treatment or the reduction of elevated ALP to normal range during treatment were associated with better OS when compared to elevated ALP values before and during treatment (p < 0.0001). High prostate‐specific antigen (PSA) level (≥100 μg/L) before radium‐223 treatment was associated with poor OS compared to low PSA level (<20 μg/L) (p = 0.0001). Most patients (57%) experienced pain relief. Pain relief indicated better OS (p = 0.002). Radium‐223 treatment was well tolerated. Toxicity was mostly low grade. Only 12.5% of the patients had grade III–IV adverse events, most commonly anemia, neutropenia, leucopenia, and thrombocytopenia. CONCLUSION: Radium‐223 was well tolerated in routine clinical practice, and most patients achieved pain relief. Pain relief, ALP normalization, lower baseline PSA, and PSA decrease during radium‐223 treatment were prognostic for better survival. The efficacy of radium‐223 in mCRPC as estimated using OS was comparable to earlier randomized trial in this retrospective real‐world study. Our results support using radium‐223 for mCRPC patients with symptomatic bone metastases even in the era of new‐generation androgen receptor‐targeted agents.