Use and Impact of Positron Emission Tomography/Computed Tomography Prior to Salvage Radiation Therapy in Men with Biochemical Recurrence After Radical Prostatectomy: A Scoping Review

Abstract

ContextThe use, common findings, and impact of modern molecular positron emission tomography (PET)/computed tomography (CT) imaging prior to salvage radiation therapy (RT) in men with biochemical recurrence after radical prostatectomy (RP) have not been evaluated comprehensively. ObjectiveWe performed a scoping systematic review of the literature assessing detection rates, detection patterns, changes in management, as well as changes in patient outcome resulting from molecular PET/CT imaging using three molecular tracers: 18F-fluciclovine, 8Ga prostate-specific membrane antigen (PSMA)-11, and 18F-DCFPyL. Evidence acquisitionA computerized bibliographic search of the Medline/PubMed database was carried out from inception to October 1, 2020. We included published reports and abstracts evaluating the utility of 1Fluciclovine, 68Ga-PSMA-11, and 18F-DCFPyL PET in the detection of recurrent disease in the post-RP, pre–salvage RT setting. Outcomes of interest were extracted and tabulated, and existing evidence was synthesized qualitatively. Evidence synthesisA total of 45 studies were included in our qualitative synthesis. Detection rates were high across most studies, and there was often a clear relationship between prostate-specific antigen (PSA) level and positive imaging findings. Though limited randomized data are available, there appears to be increased sensitivity with the use of PSMA ligands compared with fluciclovine at low PSA values. Most studies have shown that only one-third to one-half of patients with detected lesions have lesions in the prostatic fossa alone. Management changes occur in nearly 50% of patients undergoing molecular imaging, and biochemical response in patients who undergo molecular PET-based RT planning appears to be statistically superior to the response in patients who undergo conventional imaging -based RT planning alone. High biochemical responses from molecular PET–based salvage RT, ranging from 45% to 94%, did not appear to come at the expense of increased genitourinary or gastrointestinal toxicity. The presence or absence of avid lesions appears to be a strong prognostic factor. ConclusionsMolecular PET/CT imaging in the post-RP, pre–salvage RT setting often triggers management changes that result from detecting lesions in locations not typically included in consensus-driven postoperative RT fields. Ongoing trials will assess the benefit of PSMA PET in guiding salvage RT following RP and determine its impact on long-term outcomes. Patient summaryWe reviewed and reported detection rates, detection patterns, and changes in management resulting from molecular positron emission tomography/computed tomography imaging in men with biochemically recurrent prostate cancer following radical prostatectomy. Prior to the receipt of salvage radiation therapy, molecular tracers targeting prostate-specific membrane antigen appear to be especially sensitive at identifying the place where prostate cancer has come back after surgery, which can help radiation oncologists better target the recurrent disease and potentially improve the rates of cure from prostate cancer in this setting. Future studies will determine whether these imaging tools will change cure rates and side effects, but early results are promising.