Outcome after PSMA PET/CT based salvage radiotherapy in patients with biochemical recurrence after radical prostatectomy: a bi-institutional retrospective analysis

Prostate-specific membrane antigen positron emission tomography/computed tomography (PSMA PET/CT) detects prostate cancer recurrence at low PSA levels. Radiotherapy with dose escalation to the former prostate bed has been associated with improved biochemical recurrence-free survival (BRFS). Thus, we hypothesized that PSMA PET/CT-guided salvage radiotherapy leads to improved BRFS. Methods: A total of 204 consecutive patients were referred for salvage radiotherapy following radical prostatectomy. PSMA PET/CT scans were performed and patients with PSA persistence (109 patients) or evidence of distant metastases (5 patients) were excluded from this analysis. Thus, the following analysis is based on a total of 90 patients who underwent PSMA PET/CT prior to radiotherapy due to biochemical recurrence and received salvage radiotherapy. In case of PET-positive findings, antiandrogen therapy was commenced before initiation of radiotherapy. BRFS (PSA ≤ 0.2 ng/ml) was defined as the study endpoint. Results: PET-positive lesions were detected in 42/90 (47%) patients: 24/42 (27%) fossa recurrence only, 12/42 (13%) pelvic lymph nodes only and 6/42 (7%) fossa and pelvic lymph node recurrence. Median PSA before radiotherapy was 0.44 (0.11 - 6.24). Cumulatively, a total dose of 70.0 Gy (67.2 - 72 Gy) was delivered to local macroscopic tumor, 66 Gy (59.4 - 70.2 Gy) to the prostatic fossa, 60.8 Gy (54 - 66 Gy) to PET-positive lymph nodes and 50.4 Gy (45 - 50.4 Gy) to the lymphatic pathways. After a median follow-up of 23 months, BRFS was 78%. Antiandrogen therapy was ongoing in 4 patients at last follow-up. No significant difference in BRFS between PET-positive (74%) vs. PET-negative patients (82%; p>0.05) was observed at last follow-up. Two patients had late genitourinary toxicity grade 3 and no patient had gastrointestinal toxicity ≥ 3 (NCI-CTCAE v4.03). Conclusion: PSMA PET/CT-guided salvage radiotherapy is an effective and safe local treatment option. No difference in BRFS between PET-positive and PET-negative patients was observed, indicating effective targeting of PET-positive lesions. PSMA PET/CT when readily available should be offered to patients with PSA recurrence for treatment individualization.

Journal of nuclear medicine : official publication, Society of Nuclear Medicine. 2018 Jul 12 [Epub ahead of print]

Nina-Sophie Schmidt-Hegemann, Christian Stief, Tak-Hyun Kim, Chukwuka Eze, Simon Kirste, Iosif Strouthos, Minglun Li, Wolfgang Schultze-Seemann, Harun Ilhan, Wolfgang Peter Fendler, Peter Bartenstein, Anca-Ligia Grosu, Ute Ganswindt, Claus Belka, Philipp T Meyer, Constantinos Zamboglou

Ludwig-Maximilians-University (LMU), Germany., Department of Urology, University Hospital, LMU Munich, Germany., Department of Radiation Oncology, Medical Center - University of Freiburg, Faculty of Medicine, Germany., Department of Radiation Oncology, University Hospital, LMU Munich, Germany., Department of Urology, Medical Center - University of Freiburg, Faculty of Medicine, Germany., Department of Nuclear Medicine, University Hospital, LMU Munich, Germany., Department of Nuclear Medicine, University Hospital Essen, Germany., Department of Therapeutic Radiology and Oncology, Innsbruck Medical University, Austria., Department of Nuclear Medicine, Medical Center - University of Freiburg, Faculty of Medicine, Germany.

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