Significance of prostate-specific antigen kinetics after three-dimensional conformal radiotherapy with androgen deprivation therapy in patients with localized prostate cancer.

Background: To evaluate the relationship between biochemical recurrence and post-radiation prostate-specific antigen (PSA) kinetics in patients with localized prostate cancer treated by radiotherapy with various durations of androgen deprivation therapy (ADT).

Methods: We reviewed our single-institution, retrospectively maintained data of 144 patients with T1c-T3N0M0 prostate cancer who underwent three-dimensional conformal radiotherapy (3D-CRT) between December 2005 and December 2015 and 113 patients were fulfilled the inclusion criteria. In this cohort, 3D-CRT was delivered with a dose in the range from 70.0 to 72.0 Gy with ADT. All patients received ADT as concurrent regimens. Biochemical recurrence was defined on the basis of the following: "PSA nadir + 2.0 ng/ml or the clinical judgement of attending physicians". Kaplan-Meier, log-rank, and Cox regression analyses were carried out.

Results: The median follow-up period was 54.0 months. The median duration of ADT was 17 months (interquartile range, 10-24 months). There was a trend toward statistical significant correlation between post-radiation PSA decline rate of ≥ 90% and PSA recurrence (p = 0.056). The same correlation could be observed in D'Amico high-risk patients (p = 0.036). However, it was not observed between PSA nadir and PSA recurrence (p = 0.40) in univariate analysis. Furthermore, multivariate analysis showed that post-radiation PSA decline rate of ≥ 90% was a significant predictor of biochemical recurrence in patients who received radiotherapy with various durations of ADT (p = 0.044).

Conclusions: Post-radiation PSA decline rate of ≥ 90% was a prognostic factor for biochemical recurrence in localized prostate cancer patients received 3D-CRT with various durations of ADT.