Discussant Scott T. Tagawa, MD, MS, of Weill Cornell Medicine, New York, agreed that prostate-specific membrane antigen (PSMA)-targeted positron-emission tomography (PET) is the wave of the future, but data on long-term outcomes are needed, he said.

Scott T. Tagawa, MD, MS

“We are all aware of the deficiencies of imaging for patients with prostate cancer. Patients with higher-risk localized disease may have hidden metastasis not evident on current imaging methods. Knowledge of occult disease might guide therapy. Prostate cancer is different from some other tumor types because we have a sensitive and specific serum marker in prostate-specific antigen (PSA), particularly in those who have already undergone primary treatment. The biochemically recurrent disease setting is therefore an especially common unmet need when dealing with prostate cancer,” Dr. Tagawa said.

“PSMA is nearly universally expressed on prostate cancer cells, and PSMA PET is becoming a new standard of care,” he continued.

The CONDOR study, presented by Michael J. Morris, MD, of Memorial Sloan Kettering Cancer Center, New York, evaluated fluorine F-18 DCFPyL (PyL) compared with standard of truth (pathology, correlative imaging, or PSA response) in the setting of biochemical response following standard of care. “The CONDOR study showed accurate localization and excellent inter-rater concordance,” Dr. Tagawa continued. “Many studies have looked at various PSMA PET agents in the biochemical setting, including PyL and gallium-PSMA, but most did not compare with fluciclovine-PET. The randomized published trial by Calais and colleagues demonstrated superior detection rates and better inter-reader concordance for PSMA PET,” he said.

Evolving Standard of Care

“The standard of care is changing. When PSMA PET becomes available, the question of which agent to use is likely going to be based mostly upon availability. In my mind, they are similar, and any available agent is better than no PSMA scan,” he stated.

“Initially, readers will have a learning curve, but there is good background-to-tumor ratio. Nevertheless, questions remain before PSMA PET can replace serial imaging with [computed tomography/magnetic resonance imaging] and bone scan for men with metastatic disease. Also, we still do not have studies that prove that PSMA PET results influence long-term outcome,” Dr. Tagawa said. 

DISCLOSURE: Dr. Tagawa has served as a paid consultant for Sanofi, Medivation/Astellas, Dendreon, Janssen, Genentech, Bayer, Endocyte, Eisai, Immunomedics, Karyopharm, ­AbbVie, Tolmar, Seattle Genetics, Amgen, Clovis, QED, Pfizer, Advanced Accelerator Applications/Novartis, Genomic Health, Point Pharma, and Ambrx; and has received institutional research funding from Sanofi, Medivation/Astellas, Dendreon, Janssen, Amgen, Progenics, Dendreon, Lilly, Genentech, NewLink, Bristol-Myers Squibb, Inovio, AstraZeneca, Immunomedics, Atlab, Boehringer Ingelheim, Millennium, Bayer, Merck, AbbVie, Karyopharm, Seattle Genetics, and Advanced Accelerator Applications/Novartis.