Circulating Tumor Cells as a Biomarker of Survival and Response to Radium-223 Therapy: Experience in a Cohort of Patients With Metastatic Castration-Resistant Prostate Cancer

Although increasing numbers of therapies with proven survival benefits have become available for metastatic castration-resistant prostate cancer (mCRPC), including radium-223, there is still a need for reliable biomarkers that provide information about clinically meaningful outcomes and treatment responses.

This study was a translational study that was conducted prospectively by the Spanish Oncology Genito-Urinary Group and included 45 patients with histologically confirmed mCRPC who were treated with radium-223. The primary response outcome was defined by a decline in circulating tumor cells (CTCs) of > 50% from baseline or a CTC count of ≤ 5 cells/7.5 mL at cycle 3 of radium-223. We also assessed response according to prostate-specific antigen and alkaline phosphatase levels. CTCs were evaluated as prognostic factor for treatment completion with radium-223 treatment. Kaplan-Meier estimates of survival were calculated for the global population and were correlated with biomarker response outcomes.

Significantly, more patients with baseline CTC counts ≤ 5/7.5 mL, which are indicative of better prognoses, completed the 6 injections of therapy than those with CTC counts > 5 (16/22; 73% vs. 6/20; 30%, respectively; P = .012). The median overall survival was 16 months. Survival was significantly decreased in patients with baseline CTC counts > 5 cells/7.5 mL (7 months; P = .026) and baseline alkaline phosphatase levels ≥ 220 U/L (8 months; P = .028).

CTCs hold significant promise as a prognostic factor for survival and completing treatment prior to the initiation of bone-targeted radium-223 therapy. These findings may help to guide the use of radium-223 in patients with mCRPC.

Clinical genitourinary cancer. 2018 Jul 21 [Epub ahead of print]

Joan Carles, Daniel Castellano, María-José Méndez-Vidal, Begoña Mellado, María-Isabel Saez, Aránzazu González Del Alba, José-Luis Perez-Gracia, José Jimenez, Cristina Suárez, Juan M Sepúlveda, Ray Manneh, Ignacio Porras, Cristina López, Rafael Morales-Barrera, José-Ángel Arranz

Oncology Department, Vall d'Hebrón Institute of Oncology, Barcelona, Spain. Electronic address: ., Medical Oncology Department, 12 de Octubre University Hospital (CIBERONC), Madrid, Spain., Oncology Department, Maimonides Institute of Biomedical Research (IMIBIC), Reina Sofía Hospital, University of Córdoba, Córdoba, Spain., Medical Oncology Department, Hospital Clinic, IDIBAPS, Barcelona, Spain., Medical Oncology Department, Hospitales Regional y Universitario Virgen de la Victoria, Málaga, Spain., Medical Oncology Department, Son Espases University Hospital, Palma de Mallorca, Spain., Oncology Department, University Clinic of Navarra, Health Research Institute of Navarra (IDISNA), Pamplona, Spain., Molecular Oncology Laboratory, Vall d'Hebrón Institute of Oncology, Barcelona, Spain., Oncology Department, Vall d'Hebrón Institute of Oncology, Barcelona, Spain., Medical Oncology Department, 12 de Octubre University Hospital (CIBERONC), Madrid, Spain; Sociedad de Oncología y Hematología del Cesar, Colombia., Medical Oncology Department, Gregorio Marañón University Hospital, Madrid, Spain.