PSMA PET/CT Reveals that NCCN High-risk Prostate Cancer is No Longer High-risk Localized Disease
Ting Martin Ma, MD, PhD
by Daniel Spratt, MD, University of Michigan
The Will Rogers effect is prevalent across oncology but may be greatest in prostate cancer. With the wide spread use of PSA testing in the 1990s, the continual refinements of Gleason grading and the imaging expansion from CT, bone scan and MRI to now PSMA PET/CT, we have an unprecedented redistribution of what it means to be localized vs. metastatic today. Currently, the only imaging required for staging of high-risk prostate cancer is a CT (typically of the abdomen and pelvis) and a technetium bone scan.
PSMA PET/CT imaging has exploded around the world due to its much higher sensitivity and specificity compared to conventional imaging. However, the United States remains without FDA approval for this agent at the time of this article’s writing. Fortunately, based on clinical trials led out of UCLA, UCSF and other centers, I am hopeful that these molecular imaging modalities can soon be added to our toolbox to better personalize our treatments.
Representing the team out of UCLA, Ting Martin Ma, MD, PhD, presents important data in Impact of 68Ga-PSMA-11 PET/CT on Initial Staging of High-Risk Prostate Cancer Patients: Post-Hoc Analysis of a Prospective Single Center Experience on the staging impact of PSMA PET/CT in men with NCCN high-risk prostate cancer. They demonstrated that the PSMA PET/CT identified 19.7% of patients with regional PET positive nodal disease, and 9.4% with metastatic disease on PET/CT. Although these sites were not uniformly biopsy-proven sites of metastatic disease, it is probable that, based on prior data, 85-98% of these lesions are likely to be prostate cancer. Furthermore, they demonstrated that clinicopathologic variables, notably grade group 5 (Gleason Score 9-10) and >50% of biopsy cores being involved with cancer predicted for non-localized prostate cancer.
The implications of this data are thought provoking. Currently, based on trials such as RTOG 9202, it is estimated that 15-20% of men with high-risk prostate cancer will develop metastatic disease with long-term follow-up. It remains highly suggestive and probable that many of these men likely harbored pre-existing regional or metastatic disease that now can be, in part, detected by PSMA PET/CT. So, the question remains for men with no evidence of N1 or M1 disease on PSMA PET/CT, what is their natural history with current standard of care therapy? No one knows yet. Additionally, for patients with nodal or distant disease only on PSMA PET/CT, it remains unclear if they should be treated like a de novo mHSPC patient with androgen deprivation therapy (ADT), next-generation AR-signaling inhibition or chemotherapy, and treatment of the primary.
What is perplexing about this data is that the UCLA group has previously suggested that grade group 5 patients benefit the most from local dose escalation to the prostate gland. This is interesting, given their current findings demonstrate that nearly 30% of patients with grade group 5 disease have regional or distant metastatic disease. Clearly, we continue to have a lot to understand about how best to manage PSMA PET/CT detected N1 or M1 disease.
Impact of 68Ga-PSMA-11 PET/CT on Initial Staging of High-Risk Prostate Cancer Patients: Post-Hoc Analysis of a Prospective Single Center Experience was released onDemand on Sunday, October 25 in the Science Center, as part of Scientific session (SS) 09.
Published on: October 26, 2020