Postoperative elective pelvic nodal irradiation compared to prostate bed irradiation in locally advanced prostate cancer \u2013 a retrospective analysis of dose-escalated patients

Carola Link,Markus Bohrer,Frank Lohr,Patrick Honeck,Joerg Schaefer,Frank Anton Giordano,Christian Bolenz,Frederik Wenz,Daniel Buergy,Akiko Makabe

doi:10.1186/s13014-019-1301-5

Abstract

BackgroundIt is uncertain if whole-pelvic irradiation (WPRT) in addition to dose-escalated prostate bed irradiation (PBRT) improves biochemical progression-free survival (bPFS) after prostatectomy for locally advanced tumors. This study was initiated to analyze if WPRT is associated with bPFS in a patient cohort with dose-escalated (> 70 Gy) PBRT.MethodsPatients with locally advanced, node-negative prostate carcinoma who had PBRT with or without WPRT after prostatectomy between 2009 and 2017 were retrospectively analyzed. A simultaneous integrated boost with equivalent-doses-in-2-Gy-fractions (EQD-2) of 79.29 Gy or 71.43 Gy to the prostate bed was applied in patients with margin-positive (or detectable) and margin-negative/undetectable tumors, respectively. WPRT (44 Gy) was offered to patients at an increased risk of lymph node metastases.ResultsForty-three patients with PBRT/WPRT and 77 with PBRT-only were identified. Baseline imbalances included shorter surgery-radiotherapy intervals (S-RT-Intervals) and fewer resected lymph nodes in the WPRT group. WPRT was significantly associated with better bPFS in univariate (p = 0.032) and multivariate models (HR = 0.484, p = 0.015). Subgroup analysis indicated a benefit of WPRT (p = 0.029) in patients treated with rising PSA values who mostly had negative margins (74.1%); WPRT was not associated with a longer bPFS in the postoperative setting with almost exclusively positive margins (96.8%).ConclusionWe observed a longer bPFS after WPRT compared to PBRT in patients with locally advanced prostate carcinoma who underwent dose-escalated radiotherapy. In subset analyses, the association was only observed in patients with rising PSA values but not in patients with non-salvage postoperative radiotherapy for positive margins.

Highlights

It is uncertain if whole-pelvic irradiation (WPRT) in addition to dose-escalated prostate bed irradiation (PBRT) improves biochemical progression-free survival after prostatectomy for locally advanced tumors
Radiotherapy factors univariately associated with biochemical progression-free survival (bPFS) or freedom from biochemical failure (FFBF) WPRT was significantly associated with bPFS (p = 0.032) and FFBF (p = 0.033) in univariate analysis
It is impossible to distinguish benefits associated with dose escalation (p < 0.001 for bPFS and FFBF; Fig. 2a-b) from benefits associated with positive margins [25] or benefits from a negative risk selection in salvage patients; salvage vs. postoperative radiotherapy was associated with shorter bPFS and FFBF

Summary

Introduction

It is uncertain if whole-pelvic irradiation (WPRT) in addition to dose-escalated prostate bed irradiation (PBRT) improves biochemical progression-free survival (bPFS) after prostatectomy for locally advanced tumors. The addition of ADT has just recently been shown to improve biochemical progression-free survival (bPFS) [5] and overall survival (OS) after longer follow-up [6] when added to moderate-dose radiation therapy (66 and 64.8 Gy, respectively, at the lower end of most recent EU and US guideline recommendations (≥66 and ≥ 64–65 Gy [7, 8])). Interim results from the 3-arm randomized NRGOncology/RTOG-0534 trial support this approach; the study recently reported a bPFS benefit in the salvage setting by adding ADT or ADT plus WPRT to prostate bed (“fossa-only”; PBRT) irradiation [19]

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Results

Discussion

Conclusion