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Randomized Trial of 18F-fluciclovine vs. 68Ga-PSMA PET/CT Guided Post-Prostatectomy Radiotherapy: Interim Volumetric and Toxicity Analyses

2022; Elsevier BV; Volume: 114; Issue: 3 Linguagem: Inglês

10.1016/j.ijrobp.2022.07.1162

1879-355X

Vishal R. Dhere, D.M. Schuster, S. Goyal, E. Schreibmann, B. Hershatter, S.A. Patel, J.W. Shelton, S. Hanasoge, P.R. Patel, N. Sebastian, O.A. Adediran, I.O. Lawal, A. Jani,

Radiopharmaceutical Chemistry and Applications

Purpose/Objective(s) Post-prostatectomy XRT with 18 F-fluciclovine (fluciclovine) has demonstrated improved event-free survival compared to conventional imaging (CT and/or MRI) based planning. Recently, 68 Ga-PSMA (PSMA) has been explored as an alternative radiotracer. We hypothesized that both fluciclovine and PSMA would result in a) significant changes in XRT volumes and b) similar acute toxicity. Materials/Methods We conducted an IRB-approved, prospective, randomized control trial in post-prostatectomy patients with biochemical relapse comparing fluciclovine (Arm A) and PSMA (Arm B) incorporation. Target volume changes before ( pre) and after ( post) PET incorporation were assessed including: prostate bed with (CTV PLV / PTV PLV ) or without (CTV PB /PTV PB ) pelvic nodal treatment. PTV PB received 66.6Gy +/- boost up to 76Gy and PTV PLV received 45Gy +/- boost up to 56Gy. We evaluated organ-at-risk (OAR) V40Gy and V65Gy pre & post for: bladder (-CTV), rectum, penile bulb and V45Gy for small bowel. Acute provider reported (<30days) toxicity was assessed using CTCAE v5.0. Fisher's exact test & Wilcoxon signed-rank test were used. This analysis includes 100 of 140 intended patients. Results Of 100 patients accrued 23 patients were excluded for extra-pelvic uptake, consent withdrawal, pending XRT or were not yet randomized (11 Arm A & 12 Arm B) leaving 77 patients for analysis (38 Arm A & 39 Arm B). Arm A patients had significantly increased mean CTV PB (115.99cc v 116.72cc; pre v post, respectively; p<0.01); mean PTV PB (282.26cc v 286.02cc, pre v post , respectively; p<0.01), mean CTV PLV (474.58cc v 477.72cc; pre v post, respectively; p<0.01) and mean PTV PLV (1063.65cc v 1073.17cc, pre v post, respectively; p=0.01) volumes. Arm B patients had increased mean CTV PB (142.53 v 146.32cc; pre v post, respectively; p<0.01), however, there was no significant difference in mean PTV PB (p=0.18); mean CTV PLV (p=0.63); or mean PTV PLV (p=0.22) volumes. Rectal V65Gy (p<0.01) & penile bulb V40Gy & V65Gy (p<0.01) were increased in Arm A post v pre but were within trial constraints. No other OAR constraints were significantly different pre v post in either Arm. Grade 2 GU (24.32% v 11.11%, Arm A v Arm B, respectively) & GI (8.11% v 2.78%, Arm A v Arm B, respectively) toxicity was moderate; overall toxicity was not significantly different between Arms (p=0.22 v 0.74, GU & GI, respectively) with no G3+ events reported. Conclusion Both fluciclovine & PSMA guided XRT planning impacted bed target volume. Due potentially to prostate bed uptake differences (in an earlier report of the first 65 patients PET uptake was 84.4% v 39.4% for prostate bed in Arm A v B, respectively), Arm A patients had significantly increased PTV PB & PTV PLV volumes post-PET. There was no significant difference in acute toxicity between Arms. Further analyses of biochemical control and patient reported outcomes are forthcoming.