Biochemical progression-free survival in localized prostate cancer patients treated with definitive external beam radiotherapy.

Introduction: Prostate cancer is now the third most frequent noncutaneous malignancy in Iranian men and the fifth most common cancer worldwide. Measurement of total serum prostate specific antigens (PSAs) has been one of the strongest predictors of biochemical progression and overall survival in determining the efficacy of definitive external beam radiation therapy in patients with localized prostate cancer. The aim of this research was to identify the 5-year biochemical progression-free survival (BFS) and related prognostic and predictive factors of localized prostate cancer patients who were treated with definitive external beam radiotherapy.

Methods: This study analyzed 192 localized prostate cancer patients from stage T1aN0M0 to stage T3N0M0; they were treated with definitive radiation therapy and followed up in the radiation-oncology ward of Shohada-e-Tajrish Hospital in Tehran (Iran) between 2006 and 2013. The 5-year BFS was analyzed using the Kaplan-Meier estimate. For multivariate analysis, the Cox proportional hazards model was used to assess the strengths of various factors for 5-year BFS.

Results: The follow-up period was between 14-81 months, with a median of 31 months. The median cumulative prostate dose in our series was 64 Gray (Gy) (range 62 to 78 Gy). The 5-year BFS for all patients was 65.1%, and 5-year BFS in low-risk, intermediate-risk and high-risk groups were 100%, 86.5%, and 54.9% respectively. Multivariate analysis found statistically significant relation between 5-year BFS and initial PSA>20, Gleason score 8-10, high risk group, TNM stage≥T2cN0M0, radiotherapy dose<70 Gy, radiotherapy with 2D technique and hormonal therapy in high-risk group (p=0.003, p=0.032, p=0.014, p=0.001, p=0.035, p=0.035, p=0.022 respectively).

Conclusion: Our seven years' experience of follow-up with PSA showed that PSA was the strongest predictor of biochemical progression survival in patients with prostate cancer who were treated with definitive external beam radiation therapy.