Elevated serum activin A and survival in CRPC

e15170 Background: The prognosis of castration-resistant prostate cancer (CRPC) varies widely. Activin A is a ligand in the TGF-B superfamily that regulates cell proliferation, apoptosis, differentiation, and immune responses. In patients with multiple myeloma, elevated activin A is associated with advanced disease and poorer overall survival (OS). Methods: 60 Metastatic CRPC patients whose serum samples were stored at the Dana-Farber Cancer Institute were used for this study. Plasma activin A levels were measured using ELISA (R&D Systems, Minneapolis, MN). Levels of activin A within key patient and disease characteristics were analyzed using the Wilcoxon rank sum test. OS distributions by activin A tertile status were estimated with Kaplan-Meier (KM) and compared with the logrank test. Cox regression was used to produce hazard ratios (HR). Results: In this cohort of 60 patients with metastatic CRPC, median age at diagnosis was 62y, median PSA was 15.3 ng/mL and 37% had a biopsy Gleason score (GS) >8. The index blood draw was a median of 32.9 mo from androgen-deprivation therapy. Median age and PSA at blood draw were 71y and 23.5 ng/mL. At the time of blood draw, 57% of patients had bone only metastasis, 30% were receiving primary or 38% secondary hormonal therapy, and 30% were receiving chemotherapy. Median survival follow-up was 17 months after blood collection (27 deaths). Activin A levels were 621.9 pg/mL (median) and 1382.7 pg/mL (mean). Activin A levels were elevated among older patients (> 65y) and only within patients with higher PSA (>20 ng/mL) at blood draw. KM estimates of median OS (months) for the low, mid and high serum activin A tertile groups were 19.7, 13.8 and 5.4, respectively (p