Dose-Intensified Postoperative Radiation Therapy for Prostate Cancer: Long-Term Results From the PKUFH Randomized Phase 3 Trial

Abstract

PURPOSEIn the randomized, single-center, PKUFH phase III trial, dose-intensified (72 Gy) radiation therapy was compared with conventional (66 Gy) radiation therapy. In a previous study, we found no significant difference in biochemical progression-free survival (bPFS) between the two cohorts at 4 years. In the current analysis, we provide 7-year outcomes. MATERIALS AND METHODSPatients with stage pT3-4, positive surgical margins, or prostate-specific antigen increase ≥0.2 ng/mL after radical prostatectomy were randomly assigned 1:1 to receive either 72 Gy in 36 fractions or 66 Gy in 33 fractions. All the patients underwent image-guided intensity-modulated radiotherapy. The primary end point was bPFS. Secondary end points were distant metastasis-free survival (DMFS), cancer-specific survival (CSS), and overall survival (OS), as estimated using the Kaplan–Meier method. RESULTSBetween September 2011 and November 2016, 144 patients were enrolled, with 73 and 71 in the 72 and 66 Gy cohorts, respectively. At a median follow-up of 89.5 months (range, 73-97 months), there was no difference in 7-year bPFS between the 72 and 66 Gy cohorts (70.3% vs 61.2%; hazard ratio [HR] = 0.73, 95% confidence interval [CI]: 0.41-1.29; P = 0.274). However, in patients with a higher Gleason score (GS 8-10), the 72 Gy cohort had statistically significant improvement in 7-year bPFS compared with the 66 Gy cohort (66.5% vs 30.2%; HR = 0.37, 95%CI: 0.17-0.82; P = 0.012). In addition, in patients with multiple positive surgical margins (mSM+), the 72 Gy cohort had statistically significant improvement in 7-year bPFS compared with single positive surgical margin (82.5% vs 57.5%; HR = 0.36, 95%CI: 0.13-0.99; P = 0.037). The 7-year DMFS (88.4% vs 84.9%; HR = 0.93, 95%CI: 0.39-2.23; P = 0.867), CSS (94.1% vs 95.5%; HR = 1.19, 95%CI: 0.42-3.39; P = 0.745), and OS (92.8% vs 94.1%; HR = 1.29, 95%CI: 0.51-3.24; P = 0.594) had no statistically difference between the 72 and 66 Gy cohorts. CONCLUSIONThe current 7-year bPFS results confirmed our previous findings that dose escalation (72 Gy) demonstrated no improvement in 7-year bPFS, DMFS, CSS, or OS compared to the 66 Gy regimen. However, patients with a higher GS (8-10) or mSM+ might benefit from the 72 Gy regimen, but this requires further prospective research.