Real-world outcomes in patients with metastatic castration-resistant prostate cancer receiving second-line chemotherapy versus an alternative androgen receptor-targeted agent (ARTA) following early progression on a first-line ARTA in a US community oncology setting

Abstract

Objective: This retrospective observational study assessed if second-line chemotherapy vs. androgen receptor-targeted agents (ARTAs; abiraterone/enzalutamide) is associated with improved outcomes in metastatic castration-resistant prostate cancer (mCRCaP) patients who experience early progression on first-line ARTAs in a US community setting. Methods: Patients with mCRCaP (n = 345) who progressed ≤ 12 months after first-line ARTA and received second-line chemotherapy (docetaxel/cabazitaxel; n = 147) or ARTA (n = 198) between May 2011 and October 2014 were identified. Overall survival (OS), prostate-specific antigen (PSA) response and progression, and clinical response were compared for second-line chemotherapy vs. ARTA, using one-sided tests from second-line therapy initiation. Multivariate analyses were adjusted for: year, age, metastases, opioid use, Eastern Cooperative Oncology Group performance score, PSA, hemoglobin, alkaline phosphatase, lactate dehydrogenase (LDH), and albumin levels. Results: Patients receiving second-line chemotherapy vs. ARTA were younger (median: 74 vs. 79 years) and had a poorer prognosis in terms of PSA, LDH, alkaline phosphatase, albumin and hemoglobin levels, opioid use, and Halabi risk score (P < 0.05). Response rates were higher for chemotherapy vs. ARTA (PSA: adjusted odds ratio = 2.27, P = 0.005; clinical: adjusted odds ratio = 1.78; P = 0.020) and time to PSA progression was longer (adjusted hazard ratio [aHR] = 0.66; P = 0.010). A trend favored chemotherapy vs. ARTA for OS (aHR = 0.81, P = 0.148). Among patients with poor prognostic features, those receiving chemotherapy had significantly improved OS (Halabi intermediate-/high-risk score: aHR = 0.55, P = 0.009; hemoglobin < 11 g/dl: aHR = 0.41, P = 0.002; LDH > upper limit of normal: aHR = 0.18, P = 0.014; albumin < lower limit of normal: aHR = 0.42, P = 0.020). Conclusion: Following early progression on first-line ARTA, second-line chemotherapy may be more beneficial in mCRCaP compared with second-line ARTA in patients with a poor prognosis.