(UroToday.com) The 2023 European Association of Urology (EAU) annual congress held in Milan, Italy between March 10th and 13th, 2023 was host to a prostate cancer abstract session on the role of imaging and PSA density for biopsy indication and tumor staging. Dr. Otto Ettala presented the results of the PROSTAGE follow-up study evaluating how lesions without anatomical correlates detected on 18F-PSMA-1007-PSMA-PET/CTs should be interpreted.
Compared to the FDA-approved 11Ga and 18FDCFPyL radiotracers, 18F-PSMA-1007 has a longer half, a lower positron range, and is eliminated via the hepatobiliary route, which may offer unique advantages within the context of pelvic imaging given the lack of urinary excretion and thus better resolution for detection of pelvic lesions. However, 18F-PSMA-1007 PET/CTs frequently present with PSMA-avid bone lesions that lack anatomical correlates and are considered non-specific lesions, unlikely to be related to prostate cancer.
The objective of this study was to verify if PSMA-avid bone lesions observed only on 18F-PSMA-1007 PET-CT develop eventual anatomical correlates during long-term follow-up. To this end, the authors utilized data from the PROSTAGE study (NCT03537391) which prospectively enrolled 79 men with newly diagnosed, high-risk prostate cancer, defined as Grade Group 3 disease or worse, serum PSA 20 ng/ml or higher, and/or cT3 or worse. All men were recruited between 2018 and 2019 and underwent a contrast-enhanced whole body CT scan, a bone scintigraphy, and an 18F-PSMA-1007-PET/CT. Of the 79 men in this trial, 46 had PSMA-avid bone lesions, of whom 33 had no anatomical correspondence.
Among the 33 patients with PSMA-avid bone lesions without anatomical correlates, there were a total of 111 such lesions:
- Ribs: 56
- Pelvis: 27
- Spine: 12
- Sacrum: 9
- Extremities: 7
After a median follow-up of 27 months, only 4/111 lesions developed anatomical correlates, occurring in 1/56 rib lesions, 2/12 spine lesions, and 1/9 sacral lesions. The median baseline maximum standardized uptake (SUVmax) value of the 4 lesions that developed anatomical correlates was 7 (IQR: 6 to 11), compared to 4 (IQR: 4 to 7) among the 107 lesions that did not.
The authors concluded that:
- 18F-PSMA-1007-PET/CT frequently detects unspecific bone lesions, which are most likely of non-prostate cancer etiology
- This phenomenon does not appear to be limited to the ribs
- SUVmax values at baseline might be of value in interpreting the clinical significance of these lesions
- All 18F-PSMA-1007 PSMA-avid lesions without anatomical correlates should be interpreted with caution.
Presented by: Dr. Otto Ettala, MD, Department of Surgery, University of Turku, Turku, Turkey
Written by: Rashid K. Sayyid, MD, MSc – Society of Urologic Oncology (SUO) Clinical Fellow at The University of Toronto, @rksayyid on Twitter during the 2023 European Association of Urology (EAU) Annual Meeting, Milan, IT, Fri, Mar 10 – Mon, Mar 13, 2023.