PET molecular imaging helps guide treatment, improves DFS in recurrent prostate cancer
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The addition of PET molecular imaging to conventional imaging helped guide treatment decisions that led to improved DFS among men with recurrent prostate cancer, according to study results presented at the virtual ASTRO Annual Meeting.
“The decision to offer radiation after prostatectomy for patients with recurrent prostate cancer is complex,” Ashesh B. Jani, MD, FASTRO, professor in the department of radiation oncology at Winship Cancer Institute of Emory University, said during a press conference. “Failure rates in this setting remain high and there is a need for more accurate radiation therapy decision-making, as well as better treatment planning. This is an area where conventional imaging has significant limitations and is where we think there is a role for PET molecular imaging.”
The Emory Molecular Prostate Imaging for Radiotherapy Enhancement, or EMPIRE-1, trial enrolled 165 men with recurrent prostate cancer who initially underwent conventional imaging, including bone scans, CT or MRI. Researchers randomly assigned the men to either radiation therapy based upon initial treatment plans (n = 82) or to fluciclovine (Axumin, Blue Earth Diagnostics Ltd.) PET scan — in which men (n = 83) received radioactive tracers containing a synthetic amino acid — followed by a treatment plan based upon the additional findings of the scan.
Researchers compared failure rates at 3 years, which served as the study’s primary endpoint, and 4 years using the Z test. Provider-reported toxicities served as the secondary endpoint.
Median follow-up was 2.48 years overall and 3.06 years for failure-free patients.
Results showed a 3-year DFS rate of 75.5% among patients who underwent the additional PET scan compared with 63% among those who underwent conventional imaging alone (P = .003). The DFS benefit persisted at 4 years in the PET scan group (75.5% vs. 51.2%; P < .001).
Researchers observed no significant differences in provider-reported severe genitourinary or gastrointestinal adverse effects between the two groups.
“This suggests that treatment to PET-directed volumes was tolerable. We currently have patient-reported toxicity analysis pending,” Jani said.
“This is the first trial of PET over conventional imaging alone for post-prostatectomy radiation therapy, which incidentally was a single-institution study where the radiotracer was invented,” Jani added. “Inclusion of fluciclovine resulted in significant improvements in the DFS rate at 3 years. Integration of novel PET radiotracers into conventional imaging decisions and planning now warrants further study. EMPIRE-2 is a continuation of the current study and is looking at the randomization of fluciclovine vs. Ga-PSMA PET scan and allows for sites of dose escalation to areas of PET uptake. We are one-third of the way finished with that study and hope that within a few years we will be able to report the results.”
Perspective
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Jessica Karen Wong, MD, MEng
For men with recurrent prostate cancer after prostatectomy, there is little standard imaging to help guide therapy, as traditional imaging with nuclear medicine bone scan and CT often cannot detect residual prostate cancer in this scenario. Newer molecular imaging modalities such as 18F-fluciclovine PET/CT may help detect areas of residual prostate cancer and allow for tailored therapy that is directed to the known sites of disease. In the EMPIRE-1 trial, treatment directed to the areas of disease seen on 18F-fluciclovine PET/CT improved failure-free survival at 3 years and 4 years, meeting an impressively high bar for evaluating an imaging study. By determining that fluciclovine PET-directed therapy can improve outcomes, these results support the inclusion of novel PET radiotracers into treatment decision-making and radiation planning for men with prostate cancer in the salvage setting.
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Jani AB, et al. Abstract LBA-1. Presented at: American Society for Radiation Oncology Annual Meeting (virtual); Oct. 25-28, 2020.
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