(UroToday.com) Dr. Henk Luiting discussed the utility of histological confirmation for intraprostatic recurrences on PSMA PET/CT after prostate whole gland radiotherapy at the European Association of Urology (EAU) 2021 annual meeting’s detection of recurrence and salvage treatment options after primary treatment of prostate cancer session. Patients with an intraprostatic recurrence after radiotherapy can be considered for salvage therapy, however, the EAU guidelines recommend obtaining histological confirmation before salvage therapy. This recommendation, however, does not consider the diagnostic accuracy of PSMA PET/CT. In current daily clinical practice, the need to obtain histological confirmation is often deemed unnecessary as a result of the recognized high specificity of PSMA PET/CT, which currently is the modality of choice for detecting recurrences. The objective of this study was to evaluate the biopsy outcomes in patients with an intraprostatic recurrence on PSMA PET/CT after prostate whole gland radiotherapy.
There were 51 patients retrospectively included who were detected with solely an intraprostatic recurrence post-radiotherapy on PSMA PET/CT in the Netherland Cancer Institute and Erasmus MC that subsequently underwent prostate biopsies. Whole prostate radiotherapy (n=39 external beam radiotherapy and n=12 brachytherapy) was the initial curative therapy in all patients. A prostate mpMRI was performed in addition to a PSMA PET/CT in 44 patients, and information on repeat biopsy and PSMA PET/CT was collected. True positivity of PSMA PET/CT was defined as biopsy confirmed recurrence (first or repeat biopsy) or if there was radiological progression of the intraprostatic lesion on subsequent imaging.
The median PSA at the time of PSMA PET/CT was 3.7 (IQR 2.5-5.6) ng/ml, and the median time between initial radiotherapy and PSMA PET/CT was 75 (IQR 52-97) months. The initial prostate biopsy confirmed the intraprostatic recurrence in 36 (71%) patients, 6 out of 8 patients who underwent repeat biopsies were diagnosed with an intraprostatic recurrence, and 3 of 6 patients with subsequent imaging showed progression. Positive predictive value of PSMA PET/CT was 88.2%. Only 4 patients had a negative MRI (PIRADS≤2) of which 3 had a negative prostate biopsy and no progression on subsequent imaging. The positive predictive value for patients with a positive MRI (PIRADS≥3) and PSMA PET/CT was 92.5% (total 40 patients, 34 histological confirmed, 3 with radiological progression). Incorrect prostate sampling delayed the initiation of salvage therapy in 9 patients for a median delay of 9 (IQR 5-13) months.
Dr. Luiting concluded his presentation of intraprostatic recurrences on PSMA PET/CT after whole gland radiotherapy with the following concluding messages:
- A considerable number of patients with an intraprostatic recurrence on PSMA PET/CT post-radiotherapy will have a negative (initial) prostate biopsy
- Of these patients, however, most will have positive repeat prostate biopsy or radiological progression on repeat imaging
- The high positive predictive value of combined PSMA PET/CT and MRI positivity justifies the initiation of salvage focal therapy without histological confirmation to prevent unnecessary delay
- In patients without evidence of an intraprostatic recurrence on MRI histological confirmation is necessary before initiation of salvage therapies
Presenter by: Henk B. Luiting, MD, Erasmus MC, Dept. of Urology, Rotterdam, The Netherlands
Written by: Zachary Klaassen, MD, MSc – Urologic Oncologist, Assistant Professor of Urology, Georgia Cancer Center, Augusta University/Medical College of Georgia, @zklaassen_md on Twitter during the 2021 European Association of Urology, EAU 2021- Virtual Meeting, July 8-12, 2021.