ESMO Virtual Congress 2020: Clinical Factors That Are Prognostic for Survival Outcomes in Men with Metastatic Castration-Resistant Prostate Cancer Treated with Radium-223

(UroToday.com) The randomized phase 3 ALSYMPCA trial1 demonstrated an improvement in overall survival and symptomatic skeletal events for the treatment of metastatic castration-resistant prostate cancer (mCRPC) using the alpha-emitter radium-223 in patients with 2+ bony metastases, no visceral metastases, and metastatic lymph nodes < 3 cm in size. The optimal sequencing of radium-223 (Ra-223), especially in relation to docetaxel chemotherapy is unknown. There are also no clear biomarkers of response, as prostate-specific antigen PSA kinetics do not reflect disease response, though there is some suggestion that alkaline phosphatase levels may be informative. In this poster, Dr. Esmail Al-Ezzi and colleagues analyzed a retrospective single-institution cohort of mCRPC patients treated with Ra-223 to identify clinical factors that may be associated with overall survival benefit from this therapy.

In total, 150 patients were identified for analysis. Their demographics are shown below.

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The median overall survival of patients in this cohort was 14.5 months, consistent with the ALSYMPCA results. Based on univariate and multivariate analyses, the authors identified four baseline variables: ECOG performance status, alkaline phosphatase level, PSA level, and albumin level as independently associated with survival. Using these factors, they created as prognostic index model score that stratified patients into risk groups that were associated with survival, as seen below.

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The prognostic index model had an AUC of 0.762. The authors identified several post-treatment factors as significantly associated with survival with Ra-223 therapy as well. Receiving 4 or more doses of radium, hematologic toxicity, receiving systemic therapy after Ra-223, and PSA responses due to therapy were associated with survival in both univariate and multivariate analyses with p-values less than 0.05.

In summary, the authors generated a prognostic index model to predict the chance of benefitting from Ra-223 therapy and identified several pre-treatment and treatment-related factors associated with survival in this context. External validation is required prior to potential incorporation of this model into clinical decision making.

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Presented by: Esmail Al-Ezzi, MD, Division of Medical Oncology and Hematology, Princess Margaret Cancer Centre, University Health Network, Toronto, ON, Canada

Written by: Alok Tewari, MD, Ph.D., Medical Oncologist at the Dana-Farber Cancer Institute, at the 2020 European Society for Medical Oncology Virtual Congress (#ESMO20), September 19th-September 21st, 2020

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