68Ga-PSMA-11 PET/CT Mapping of Prostate Cancer Biochemical Recurrence After Radical Prostatectomy

68Ga-PSMA-11 PET/CT Mapping of Prostate Cancer Biochemical Recurrence After Radical Prostatectomy in 270 Patients with a PSA Level of Less Than 1.0 ng/mL: Impact on Salvage Radiotherapy Planning.

Target volume delineations for prostate cancer (PCa) salvage radiotherapy (SRT) after radical prostatectomy are usually drawn in the absence of visibly recurrent disease. 68Ga-labeled prostate-specific membrane antigen (PSMA-11) PET/CT detects recurrent PCa with sensitivity superior to standard-of-care imaging at serum prostate-specific antigen (PSA) values low enough to affect target volume delineations for routine SRT.

Our objective was to map the recurrence pattern of PCa early biochemical recurrence (BCR) after radical prostatectomy with 68Ga-PSMA-11 PET/CT in patients with serum PSA levels of less than 1 ng/mL, determine how often consensus clinical target volumes (CTVs) based on the Radiation Therapy Oncology Group (RTOG) guidelines cover 68Ga-PSMA-11 PET/CT-defined disease, and assess the potential impact of 68Ga-PSMA-11 PET/CT on SRT.
Methods: This was a post hoc analysis of an intention-to-treat population of 270 patients who underwent 68Ga-PSMA-11 PET/CT at 4 institutions for BCR after prostatectomy without prior radiotherapy at a PSA level of less than 1 ng/mL. RTOG consensus CTVs that included both the prostate bed and the pelvic lymph nodes were contoured on the CT dataset of the PET/CT image by a radiation oncologist masked to the PET component. 68Ga-PSMA-11 PET/CT images were analyzed by a nuclear medicine physician. 68Ga-PSMA-11–positive lesions not covered by planning volumes based on the consensus CTVs were considered to have a potential major impact on treatment planning.
Results: The median PSA level at the time of 68Ga-PSMA-11 PET/CT was 0.48 ng/mL (range, 0.03–1 ng/mL). One hundred thirty-two of 270 patients (49%) had a positive 68Ga-PSMA-11 PET/CT result. Fifty-two of 270 (19%) had at least one PSMA-11–positive lesion not covered by the consensus CTVs. Thirty-three of 270 (12%) had extrapelvic PSMA-11–positive lesions, and 19 of 270 (7%) had PSMA-11–positive lesions within the pelvis but not covered by the consensus CTVs. The 2 most common 68Ga-PSMA-11–positive lesion locations outside the consensus CTVs were bone (23/52, 44%) and perirectal lymph nodes (16/52, 31%). Conclusion: Post hoc analysis of 68Ga-PSMA-11 PET/CT implied a major impact on SRT planning in 52 of 270 patients (19%) with PCa early BCR (PSA < 1.0 ng/mL). This finding justifies a randomized imaging trial of SRT with or without 68Ga-PSMA-11 PET/CT investigating its potential benefit on clinical outcome.

J Nucl Med February 1, 2018 vol. 59 no. 2 230-237

Jeremie Calais1, Johannes Czernin1, Minsong Cao2, Amar U. Kishan2, John V. Hegde2, Narek Shaverdian2, Kiri Sandler2, Fang-I Chu2, Chris R. King2, Michael L. Steinberg2, Isabel Rauscher3, Nina-Sophie Schmidt-Hegemann4, Thorsten Poeppel5, Philipp Hetkamp5, Francesco Ceci1, Ken Herrmann1,5, Wolfgang P. Fendler1,6, Matthias Eiber1,3 and Nicholas G. Nickols2,7

Author Affiliations
1 Ahmanson Translational Imaging Division, Department of Molecular and Medical Pharmacology, UCLA, Los Angeles, California
2 Department of Radiation Oncology, UCLA, Los Angeles, California
3 Department of Nuclear Medicine, Klinikum rechts der Isar, Technical University of Munich, Munich, Germany
4 Department of Radiation Oncology, University Hospital, LMU Munich, Munich, Germany
5 Department of Nuclear Medicine, Universitätsklinikum Essen, Essen, Germany
6 Department of Nuclear Medicine, Ludwig-Maximilians-University, Munich, Germany; and
7 Department of Radiation Oncology, VA Greater Los Angeles Healthcare System, Los Angeles, California

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