Randomized Trial of Conventional Versus Conventional Plus Fluciclovine (18F) Positron Emission Tomography/Computed Tomography–Guided Postprostatectomy Radiation Therapy for Prostate Cancer: Volumetric and Patient-Reported Analyses of Toxic Effects

Abstract

Postprostatectomy radiation therapy planning with fluciclovine (18F) positron emission tomography (PET)/computed tomography has demonstrated improved disease-free survival over conventional only (computed tomography- or magnetic resonance imaging-based) treatment planning. We hypothesized that incorporating PET would result in larger clinical target volumes (CTVs) without increasing patient-reported toxic effects. From 2012 to 2019, 165 postprostatectomy patients with detectable prostate-specific antigen were randomized (arm 1 [no PET]: 82; arm 2 [PET]: 83). Prostate bed target volumes with (CTV1: 45.0-50.4 Gy/1.8 Gy) or without (CTV2/CTV: 64.8-70.2 Gy/1.8 Gy) pelvic nodes, as well as organ-at-risk doses, were compared pre- versus post-PET (arm 2) using the paired t test and between arms using the t test. Patient-reported outcomes used International Prostate Symptom Score and Expanded Prostate Cancer Index Composite for Clinical Practice (EPIC-CP). Univariate and multivariable analyses were performed and linear mixed models were fitted. Median follow-up of the whole cohort was 3.52 years. All patients had baseline patient-reported outcomes, 1 patient in arm 1 and 3 patients in arm 2 withdrew, and 4 arm 2 patients had extrapelvic uptake on PET with radiotherapy aborted, leaving 81 (arm 1) and 76 patients (arm 2) for analysis of toxic effects. Mean CTV1 (427.6 vs 452.2 mL; P=.462, arm 1 vs arm 2) and CTV2/CTV (137.18 vs 134.2 mL; P=.669) were similar before PET incorporation. CTV1 (454.57 vs 461.33 mL; P=.003) and CTV2/CTV (134.14 vs 135.61 mL; P < .001) were modestly larger after PET incorporation. Although V40 Gy (P=.402 and P=.522 for rectum and bladder, respectively) and V65 Gy (P=.157 and P=.182 for rectum and bladder, respectively) were not significantly different pre- versus post-PET, penile bulb dose significantly increased post-PET (P < .001 for both V40 Gy and V65 Gy). On univariate and multivariable analyses, arm was not significant for any EPIC-CP subdomain. International Prostate Symptom Score and EPIC-CP linear mixed models were not significantly different between arms. Despite larger CTVs after incorporation of fluciclovine (18F) PET, we found no significant difference in patient-reported toxic effects with long-term follow-up.