Abstract
708
Objectives: PET imaging targeting the prostate specific membrane antigen (PSMA) has been shown to have a higher sensitivity and specificity compared to conventional imaging. The objective of this study was to evaluate the impact of PSMA PET on the management of prostate cancer patients with biochemical recurrence following definitive local therapy.
Methods: 107 patients with recurrence prostate cancer were imaged using Ga-68-PSMA-11 PET. 54 patients were imaged using PET/CT and 53 patients using PET/MRI. 93 patients received Lasix injections concurrent with radiotracer administration. Patients were imaged using either a GE Discovery VCT or a GE Signa 3.0T PET/MRI. Referring clinicians filled out a pretreatment management form and a management form based on the imaging results. Changes in management were graded as major, minor, no change or unknown based upon the responses.
Results: 107 patients were imaged with biochemical recurrence as part of this protocol. The average PSA in the population was 6.2 ± 11.0 ng/mL with an average doubling time of 12.8 ± 10.8 months, and 50 patients had a PSA of less than 2.0 at the time of imaging. The average time between prior treatment and imaging (RP and/or radiation) was 4.8 ± 5.2 years, with 48 patients being imaged within two years of their most recent treatment. 38 patients had a prior prostatectomy, 38 prior radiation, and 28 patients had both prior prostatectomy and radiation. 87 patients (81%) had disease localized on PSMA imaging. Of the 107 patients imaged, 57 (53%) of the imaging studies resulted in a major change in management. The most common major change was converting from active surveillance to radiation therapy (17 patients, 16%), changing from ADT to radiation therapy (14 patients, 13%), and converting from radiation therapy to either active surveillance (4 patients, 4%) or to ADT alone (2 patients, 2%). 9 patients (8%) had a minor change, 29 patients (26%) had no change, and 12 patients (11%) had an unknown change in management.
Conclusion: The results of our surveys demonstrate a substantial impact of PSMA PET on the intended patient management. The majority of changes involved converting a targeted therapy to systemic treatment or systemic treatment to a targeted therapy. Prospective studies are warranted to determine whether directed treatment towards PSMA-avid lesions affects long-term disease outcomes. Figure 1: Example patient who converted from ADT to external beam radiation therapy. 73-year-old man with biochemical recurrence nine years after a prostatectomy, now with a PSA of 8.6. PSMA-11 PET/MRI demonstrates focal uptake in a remnant right seminal vesicle. Given the patient’s localized disease, the management was changed from systemic ADT for castration sensitive disease to external beam radiation therapy targeting his recurrence.