PSA Bounce After Dose-Escalated External Beam Radiation Therapy Is an Independent Predictor of PSA Recurrence, Metastasis, and Survival in Prostate Adenocarcinoma Patients

International Journal of Radiation Oncology Biology Physics

5 years ago

PSA Bounce After Dose-Escalated External Beam Radiation Therapy Is an Independent Predictor of PSA Recurrence, Metastasis, and Survival in Prostate Adenocarcinoma Patients

Post-treatment PSA bounce (PSA-B) is well recognized and reported in 15%-30% of prostate adenocarcinoma patients treated with radiotherapy. We evaluated the difference in PSA recurrence-free (PSA-RFS), distant metastasis–free (DMFS), overall (OS), and cancer-specific (CSS) survival between PSA bounce (PSA-B) and non-bounce patients treated with dose-escalated external beam radiotherapy (DE-EBRT).

Materials/Methods

During 1990-2010, 1898 prostate adenocarcinoma patients were treated with DE-EBRT to ≥75 Gy with ≥5 years follow-up. Patients receiving neoadjuvant/concurrent androgen-deprivation therapy (n=1035) or with less than four PSA values obtained 6 months or more after post-EBRT completion (n=87) were excluded. The evaluable 776 patients were treated (median, 81.0 Gy). PSA-B was defined as a ≥0.2 ng/mL increase above the interval PSA nadir followed by a decrease to nadir or below. PSA relapse (PSA-R) was defined as post-RT PSA nadir + 2 ng/mL. Median follow-up was 9.2 years (IQR, 5.3-10.6 years).

Results

One hundred twenty-three patients (15.9%) experienced PSA-B after DE-EBRT at a median of 24.6 months (IQR, 16.1-38.5 months). On multivariate analysis, younger age (P=0.001), lower Gleason score (P=0.0003), and higher RT dose (P=0.0002) independently predicted PSA-B. PSA-B was independently associated with decreased risk for PSA relapse (HR, 0.53; 95% CI, 0.33-0.85; P=0.008), distant metastatic disease (HR, 0.34; 95% CI, 0.12-0.94; P=0.04), and all-cause mortality (HR, 0.53; 95% CI, 0.29-0.96; P=0.04) on multivariate Cox analysis. As all 50 prostate cancer–specific deaths in patients without PSA-B were in the non-bounce cohort, competing-risks analysis was not applicable. Nonparametric competing-risks test demonstrated that patients with PSA-B had superior cancer specific survival compared to patients without PSA-B (P=0.004)

Conclusions

Patients treated with dose-escalated radiotherapy for prostate adenocarcinoma who experience post-treatment PSA-B have improved PSA-RFS, DMFS, OS, and CSS outcomes.

Teaser

In a cohort of 1898 patients treated with a uniform external-beam radiation therapy treatment approach for prostate cancer, prostate-specific antigen (PSA) fluctuations were carefully evaluated to determine their impact on long-term survival outcomes. Multivariate analysis demonstrated that the occurrence of a PSA bounce in the follow-up period predicted for reduced PSA recurrences, decreased incidence of distant metastases, and improved cause-specific and overall survival outcomes.

Publisher URL: www.sciencedirect.com/science

DOI: S0360301617338543