Evaluation of Neuroendocrine Differentiation as a Potential Mechanism of Tumor Recurrence Following Radiotherapy

This is a pilot study to test a hypothesis that a greater increase in serum chromogranin A (CgA) after a definitive radiotherapy (RT) with or without androgen deprivation therapy (ADT) is associated with a higher risk of prostate cancer recurrence after RT. Serum CgA level is measured before the start of RT and/or the start of neoadjuvant ADT for patients undergoing a definitive RT with or without ADT. CgA is also measured at various pre-defined post-RT time points. The study will analyze the followings: 1. Change in CgA level at various pre-defined post-RT time points from the baseline, 2. Correlation between the extent of post-therapy CgA change and Gleason score of malignancy, 3. Correlation between the extent of post-therapy CgA change and treatment outcome.