Impact of (68)Ga-PSMA PET/CT on salvage radiotherapy planning in patients with prostate cancer and persisting PSA values or biochemical relapse after prostatectomy

Salvage radiotherapy (SRT) is clinically established in prostate cancer (PC) patients with PSA persistence or biochemical relapse (BCR) after prior radical surgery. PET/CT imaging prior to SRT may be performed to localize disease recurrence. The recently introduced (68)Ga-PSMA outperforms other PET tracers for detection of recurrence and is therefore expected also to impact radiation planning. Forty-five patients with PSA persistence (16 pts) or BCR (29 pts) after prior prostatectomy, scheduled to undergo SRT of the prostate bed, underwent (68)Ga-PSMA PET/CT. The median PSA level was 0.67 ng/ml. The impact of (68)Ga-PSMA PET/CT on the treatment decision was assessed. Patients with oligometastatic (≤5 lesions) PC underwent radiotherapy (RT), with the extent of the RT area and dose escalation being based on PET positivity.

Suspicious lesions were detected in 24/45 (53.3 %) patients. In 62.5 % of patients, lesions were only detected by (68)Ga-PSMA PET. Treatment was changed in 19/45 (42.2 %) patients, e.g., extending SRT to metastases (9/19), administering dose escalation in patients with morphological local recurrence (6/19), or replacing SRT by systemic therapy (2/19). 38/45 (84.4 %) followed the treatment recommendation, with data on clinical follow-up being available in 21 patients treated with SRT. All but one showed biochemical response (mean PSA decline 78 ± 19 %) within a mean follow-up of 8.12 ± 5.23 months.

(68)Ga-PSMA PET/CT impacts treatment planning in more than 40 % of patients scheduled to undergo SRT. Future prospective studies are needed to confirm this significant therapeutic impact on patients prior to SRT.

EJNMMI research. 2016 Oct 26 [Epub]

Christina Bluemel, Fraenze Linke, Ken Herrmann, Iva Simunovic, Matthias Eiber, Christian Kestler, Andreas K Buck, Andreas Schirbel, Thorsten A Bley, Hans-Juergen Wester, Daniel Vergho, Axel Becker

Department of Nuclear Medicine, University Hospital Würzburg, Würzburg, Germany. ., Department of Radiation Oncology, Klinikum Ansbach, Ansbach, Germany., Department of Molecular and Medical Pharmacology, David Geffen School of Medicine at UCLA, Los Angeles, USA., Department of Urology, University Hospital Würzburg, Würzburg, Germany., Department of Diagnostic and Interventional Radiology, University Hospital Würzburg, Würzburg, Germany., Department of Nuclear Medicine, University Hospital Würzburg, Würzburg, Germany., Pharmaceutical Radiochemistry, Technische Universität München, Munich, Germany.