Dr. Briganti notes that PET vs conventional imaging in primary staging has a higher sensitivity for secondary lesions and is able to detect small lesions earlier, but he questions whether this leads to real change in treatment strategy or if there is a real benefit for patients. According to Dr. Briganti, there are several scenarios that need to be considered:
1. Patient-based analysis: Identify all patients with metastatic sites à should we abandon treatment of the primary or should we treat systemically? à We don’t know! Evidence supports systemic treatment and/or local treatment in the presence of positive conventional imaging
2. Lesions-based analysis: Identify all metastatic deposits à Should we treat all that we can see? à We don’t know! This has never been demonstrated in the primary setting
The role of PET/CT according to the guidelines in primary staging is still unclear. This is not because of a lack of resources: Dr. Briganti notes that there are at least 10 available tracers, most commonly 11C-choline and 68Ga-PSMA. In a recently published consensus on molecular imaging and theranostics in prostate cancer1, there were two key statements: (i) prostate cancer-targeted PET was considered necessary in a minority of patients based on risks and symptoms (17 of 21 panelists); (ii) if prostate cancer-targeted PET is performed at staging, then PSMA is the preferred tracer (19 of 21 panelists).
Dr. Briganti notes that 68Ga-PSMA PET has superior sensitivity, specificity, and accuracy in both the patient-based and template-based setting compared to conventional imaging. According to a recent report, the size of nodal metastasis in contemporary patients detected by 68Ga-PSMA PET is predominantly small nodal metastases: 2-5 mm (52.8%), 5-9.9 mm (23.6%), 10-20 mm (13%), and >20 mm (10.6%)2. When incorporated into a multivariable model predicting the risk of BCR, the presence of a PSMA positive pelvic lymph node was more predictive of persistent disease than cT-stage, PSA and Gleason score.
Dr. Briganti feels that changes in patient management based on the PSMA PET/CT findings is a weak clinical endpoint. In a study of 108 intermediate and high-risk patients undergoing PSMA PET/CT, management change occurred in only 21% of patients3, but to Dr. Briganti’s point: management changes are secondary to subjective clinician judgment. Generally, according to Dr. Briganti, high-risk locally advanced patients are either going to get RP + PLND or RT + ADT and at this point in time, PSMA PET/CT is not changing the management for these patients.
Dr. Briganti points to several ongoing prospective level 1 studies assessing the impact of surgery in the oligometastatic setting as the potential to change the treatment paradigm. He concluded by quoting the EAU guidelines noting: well-designed controlled trials evaluating the management and outcomes of patients with and without metastases detected by choline PET/CT, MRI, and PSMA PET/CT are needed before the decision can be made to treat patients or not based on the results of these trials.
Presented by: Alberto Briganti, Deputy Director, Urological Research Institute, Head of Prostate cancer Unit, Associate professor, Università Vita Salute, IRCCS Ospedale San Raffaele, Milan, Italy
Written by: Zachary Klaassen, MD, MSc – Assistant Professor of Urology, Georgia Cancer Center, Augusta University/Medical College of Georgia, Twitter: @zklaassen_md, at the 16th Meeting of the European Section of Oncological Urology, #ESOU19, January 18-20, 2019, Prague, Czech Republic
1. Fanti S, Minozzi S, Antoch G, et al. Consensus on molecular imaging and theranostics in prostate cancer. Lancet Oncol 2018 Dec;19(12):e696-e708.
2. van Leeuwen PJ, Emmett L, Ho B, et al. Prospective evaluation of 68Gallium-prostate-specific membrane antigen positron emission tomography/computed tomography for preoperative lymph node staging in prostate cancer. BJU Int 2017 Feb;119(2):209-215.
3. Roach PJ, Francis R, Emmett L, et al. The Impact of 68Ga-PSMA PET/CT on Management Intent in Prostate Cancer: Results of an Australian Prospective Multicenter Study. J Nucl Med 2018 Jan;59(1):82-88.