Survival outcomes of dose-escalated external beam radiotherapy (DE-EBRT) versus combined brachytherapy for intermediate- and high-risk prostate cancer using the National Cancer Data Base.

Abstract

7 Background: The purpose was to evaluate survival outcomes between dose-escalated external beam radiotherapy (DE-EBRT) versus EBRT plus brachytherapy for intermediate- and high-risk prostate cancer, using the National Cancer Data Base (NCDB). Methods: Patients with cN0M0 prostate cancer treated from 2004-2006, with available data for radiation therapy dose were included. Radiation treatment comparison groups were the following: EBRT alone (75.6-81 Gy) and EBRT (40-50.4 Gy) plus brachytherapy, with EBRT delivered in 1.8-2.0 Gy per fraction. Eligible patients had known T-stage, prostate-specific antigen, Gleason score, and receipt of androgen deprivation therapy. Results: A total of 20,279 patients with intermediate (n = 12,617) and high-risk (n = 7,662) prostate cancer were included; 71.3% (n=14,452) received EBRT alone, 28.7% (n = 5,827) received EBRT plus brachytherapy. Median follow up was 82 months (range, 3-120 months) and median age was 70 years (36-90 years). By multivariate analysis, EBRT plus brachytherapy had a significantly improved survival benefit (hazard ratio [HR], 0.75; p < 0.001) compared to EBRT alone (75.6-81 Gy); this significance remained consistent for both intermediate-risk (HR, 0.73; p < 0.001) and high-risk (HR, 0.76; p < 0.001) when analyzed separately. On subset analysis however, EBRT plus brachytherapy did not have a significant survival improvement (HR, 0.91; p = 0.083) when compared to very high dose EBRT alone (79.2-81 Gy) for all patients combined; this persisted for intermediate-risk (HR, 0.73; p = 0.062) and high-risk (HR, 0.93; p = 0.400) patients when analyzed separately. Conclusions: Patients receiving EBRT plus brachytherapy had improved survival compared to DE-EBRT alone (75.6-81 Gy) for intermediate- and high-risk prostate cancer. When comparing EBRT plus brachytherapy versus very high dose EBRT alone (79.2-81 Gy), this survival advantage disappeared. Given these findings, intermediate- and high-risk prostate cancer patients may benefit from EBRT plus brachytherapy compared with DE-EBRT alone; however, very high doses of EBRT may also be an equivalent option.