Real-world outcomes in patients (pts) with metastatic castration-resistant prostate cancer (mCRPC) receiving second-line (2L) chemotherapy (CT) vs alternative androgen receptor-targeted agents (ARTA) after lack of response to first-line (1L) ARTA in US community oncology practices.

Abstract

214 Background: The relationship between treatment sequence and mCRPC outcomes is unclear. This retrospective study assessed if 2L CT vs alternative ARTA is associated with improved outcomes in pts with lack of response to 1L ARTA in the US community oncology setting. Methods: Using Altos electronic medical records, we identified 345 mCRPC pts with lack of response to 1L ARTA (abiraterone or enzalutamide) who received 2L docetaxel or cabazitaxel (CT cohort N = 147), or alternative ARTA (ARTA cohort N = 198) from May 2011 to Oct 2014. Outcomes were evaluated from start of 2L therapy and compared for 2L CT vs ARTA cohorts using one-sided tests. Prostate-specific antigen (PSA) response ( ≥ 50% reduction) and overall survival (OS) were assessed using logistic and Cox proportional hazard regression models adjusted for year, age, metastases, opioid use, ECOG performance score, PSA, hemoglobin (Hb), alkaline phosphatase (ALP), lactate dehydrogenase (LDH) and albumin (Alb) levels. Results: At start of 2L therapy, pts receiving CT vs ARTA were younger (median age, 74 vs 79 yr) and had a worse prognosis: higher mean PSA (439 vs 231 ng/mL), LDH (344 vs 234 U/L) and ALP (241 vs 166 U/L), lower mean Hb (11 vs 12 g/dL), higher mean Halabi risk score (159 vs 137; JCO 2014:32;671–7), increased opioid use (42 vs 22%), and more pts had Alb < lower limit of normal (LLN; 25 vs 15%); all p < 0.01. More pts in the CT vs ARTA cohort had a PSA response (adjusted odds ratio = 2.27, p = 0.005) and there was a non-statistically significant trend toward improved OS for 2L CT vs ARTA (adjusted hazard ratio [aHR] = 0.81, p = 0.148). Among pts with poor prognostic features, those in the CT cohort had significantly improved OS (Halabi intermediate–high risk score: aHR = 0.55 p = 0.009; Hb < 11 g/dL: aHR = 0.41 p = 0.002; LDH > upper limit of normal: aHR = 0.18 p = 0.014; Alb < LLN: aHR = 0.42 p = 0.020), compared with those in the ARTA cohort. Conclusions: Treatment with 2L CT, vs 2L ARTA, may be more suitable for pts with a lack of response to 1L ARTA, particularly in pts with a poor prognosis. Funding: Sanofi Genzyme.