ESOU 2019: Reliability of PET/CT in Primary Staging of Prostate Cancer

Prague, Czech Republic (UroToday.com) Dr. Alberto Briganti from Milan started this locally advanced prostate cancer session by delivering this keynote address discussing the reliability of PET/CT in the primary staging of prostate cancer.

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

References:
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.
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