Association of prostate specific-antigen doubling time (PSADT) with metastasis-free survival (MFS) and overall survival (OS) in non-metastatic castration-resistant prostate cancer (nmCRPC).

Abstract

e16525 Background: For optimal nmCRPC management, it is important to assess the rate of disease progression and its predictors. MFS and OS endpoints are likely to be important determinants in evaluating the relative impact of treatments in nmCRPC patients. This study assessed the association of PSADT with MFS and OS in real world practice. Methods: A retrospective cohort study of men ≥18 years old was conducted using the Optum electronic health record (EHR) database (2007-2016). nmCRPC was defined as a prostate cancer diagnosis, no ICD-9/10 code or therapy indicating metastatic disease, a testosterone (T) level < 50 ng/dL (castrate level) and 2 rising PSAs (relative rise ≥25%; absolute rise ≥2 ng/mL above nadir) ≥1 week apart. Baseline PSADT, calculated from the PSA nadir until 2nd rise of PSA, was grouped into < 6, 6-18 or > 18 months. A Cox proportional hazard model was used to assess the association of baseline PSADT with MFS and OS, comparing PSADT < 6 and 6-18 months against PSADT > 18 months. Multivariable analysis was adjusted for age, race, comorbidity index score, T levels, therapy and bone scans before nmCRPC. A linear trend was tested by taking PSADT as a continuous variable (median value in each group) in the model. Results: A total of 901 patients were identified. Mean nmCRPC onset age was 76 years and mean follow-up time was 2 years. The median PSADT was 7 months, ranging from 0.5 to 267 months. During follow-up, 477 patients developed metastasis and 384 died. MFS was 89%, 60%, and 47% at year 1, 3 and 5, respectively. Men with PSADT < 6 and 6-18 months had ≥50% increased risk of shorter MFS than men with PSADT > 18 months; hazard ratios (HR) were 1.87 (95% confidence interval [CI]: 1.39-2.54) and 1.50 (95%CI: 1.11-2.04), respectively. OS was 87%, 64% and 57% at year 1, 3 and 5, respectively. Shorter PSADT was associated with shorter OS (p for trend < 0.001). Men with a PSADT < 6 months had a 2-fold increased risk for decreased OS (HR = 2.04, 95% CI: 1.44-2.90). Conclusions: Patients with nmCPRC with shorter PSADT had significantly shorter MFS and OS compared to those with longer PSADT. Baseline PSADT may serve as a predictor for nmCRPC progression.