Utility of serum prostate specific antigen doubling time (PSADT) in patients with androgen independent prostate cancer

Abstract

4631 Background: Patients who fail androgen deprivation therapy and have a rise in serum PSA are coined as having Androgen Independent Prostate Cancer (AIPC). These patients are treated with second line hormones or chemotherapy. Chemotherapy has significant palliative benefits; and a small survival advantage in asymptomatic patients, but may adversely impact quality of life. It is unclear when asymptomatic patients should be offered chemotherapy. Serum PSA has been accepted as a surrogate marker of response in patients with advanced prostate cancer. PSA doubling time (PSA DT) may accurately reflect the biology of the disease more than serum PSA measurements alone. We retrospectively evaluated the use of PSADT to predict outcome and help guide timing of chemotherapy initiation in patients with AIPC. Methods: Institutional Review Board at Stanford approved of this retrospective review. Patient population included those patients seen at Stanford from 2001–2004 with androgen independent prostate cancer. Data was collected in 118 patients. Patient characteristics were obtained and data analyzed. Serum PSA at multiple time points were obtained and corresponding symptoms of bone pain was obtained. PSA DT was calculated using the natural log of 2 divided by the slope of the linear regression of log PSA with time. Overall survival was calculated from the time of AIPC to death or last follow up. Results: Ninety patients were evaluable. Median age of patients was 67; mean PSA was 129; 74 patients (82%) had bone metastases, 54(60%) were symptomatic. There were more patients receiving chemotherapy who were symptomatic (P=.01). There was a trend in superior overall survival in the group that were asymptomatic (P=.06). Among the asymptomatic patients PSA DT of 3 months correlated with superior survival (P=.0083). Among the asymptomatic patients given chemotherapy there was a superior survival in the patients who had a PSADT of >3 months (P=.01).A PSA DT of <1 month predicted for clinical symptoms (P=.05) Conclusion: A PSADT of 3 months is helpful in guiding timing of chemotherapy. It may be a prognostic tool to include in patients with AIPC. No significant financial relationships to disclose.