198 - Patient-Reported Outcomes in a Randomized Trial of <sup>18</sup>F-Fluciclovine vs<sup>68</sup>Ga-PSMA-11 PET/CT-Guided Post-Prostatectomy Radiation with Simultaneous Integrated Boosts

11:35am - 11:45am PT

Room 156/158

Presenter(s)

Ashesh Jani, MD, MS, FASTRO - Emory University, Atlanta, GA

V. R. Dhere¹, D. M. Schuster², S. Goyal³, E. Schreibmann¹, N. Sebastian¹, S. A. Patel⁴, S. Hanasoge⁴, J. W. Shelton¹, P. R. Patel¹, B. Hershatter¹, O. Abiodun-ojo⁵, I. O. Lawal⁵, and A. Jani¹; ¹Department of Radiation Oncology, Winship Cancer Institute of Emory University, Atlanta, GA, ²Department of Radiology and Imaging Sciences, Emory University, Atlanta, GA, ³Department of Biostatistics and Bioinformatics Shared Resource, Winship Cancer Institute, Atlanta, GA, ⁴Department of Radiation Oncology, Emory University, Atlanta, GA, ⁵Emory University, Atlanta, GA

Purpose/Objective(s):

We conducted a randomized trial comparing ¹⁸F-Fluciclovine (fluciclovine) and ⁶⁸Ga-PSMA-11 (PSMA) PET/CT-guided post-prostatectomy radiation (XRT) with simultaneous integrated boosts to sites of PET uptake. Provider-assessed toxicity was mild with no grade 3+ events. We hypothesized that patient-reported outcomes (PROs) would 1) be similar between the two arms and 2) not significantly higher in pts receiving simultaneous integrated boosts (SIBs).

Materials/Methods:

140 pts with detectable PSA after prostatectomy and negative standard imaging were enrolled on an IRB approved trial and randomized to fluciclovine (Arm 1) or PSMA (Arm 2)-guided post-prostatectomy radiation. Treatment volumes were rigidly defined on protocol based on PET uptake: none/prostate bed (PB)= PB XRT (66.6 Gy/1.8 Gy fxs); pelvic lymph node (PLN) uptake or pathologically involved PLN: PB+PLN (45.0 Gy/1.8 Gy fxs) XRT. Use of SIB was at the discretion of the treating physician and generally employed when organ-at-risk constraints were met. Toxicity [baseline, acute, max late (=90 days), most recent] was assessed using American Urologic Association Symptom Score (AUA) (0-35, higher scores indicating worse toxicity) and Expanded Prostate Cancer Index Composite for Clinical Practice (EPIC-CP) [0-12 per subdomain (incontinence, urinary irritation, bowel, sexual, hormonal), with higher scores indicating worse toxicity]. Minimal clinically important difference (MCID) was defined as half a standard deviation of the baseline score. Linear mixed models (LMMs) were performed to analyze PRO changes over time, comparing the two arms.

Results:

59 fluciclovine and 60 PSMA pts received radiation on study and were included for analysis; 50/59 fluciclovine and 31/60 PSMA pts received SIB (median: 74G/2Gy fx for PB; 55Gy/2.2Gy fx for PLN). Median follow-up was 2.0 years. AUA scores were not significantly different between Arms at any timepoint; mean AUA change from baseline to most recent was +1.3 points in each Arm, which was under the MCID threshold (2.9). There were no differences in EPIC-CP subdomain scores between Arms at any time point; mean EPIC-CP change from baseline to most recent did not exceed MCID for any subdomain except for irritative score in Arm 2 (+0.94, MCID 0.83). Use of SIB (vs no SIB) was not associated with higher AUA or EPIC-CP domain score at any timepoint. Among pts receiving an SIB, the vitality score increased by 0.97 (MCID 0.89) from baseline to the most recent assessment; no other subdomain score changes exceeded the MCID.

Conclusion:

There were no significant differences in PROs between Arms, and use of SIB was not associated with increased AUA or EPIC-CP score. Previously reported provider-assessed toxicity was similarly mild, suggesting that SIB dose escalation to sites of PET positivity is well-tolerated if plans adhere to OAR constraints.