To evaluate 18F-labeled-fluorodeoxyglucose (18F-FDG-) and 18F-labeled-sodium fluoride (18F-NaF-) positron emission tomography/computed tomography (PET/CT) as biomarkers in metastatic castrate-resistant prostate cancer (mCRPC).
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Nine men (53-75 years) in a phase 1 trial of abiraterone and cabozantinib had 18F-FDG-PET/CT, (18)F-NaF-PET/CT and standard imaging (99mTc-labeled-methylene-diphosphonate (99mTc-MDP) bone scan and abdominal/pelvic CT) at baseline and after 8 weeks of therapy. Baseline disease was classified as widespread 18F-FDG-avid, oligometastatic 18F-FDG-avid (1 site), or non-18F-FDG-avid. Metabolic response was classified using European Organisation for Research and Treatment of Cancer (EORTC) criteria. Treatment response using Response Evaluation Criteria in Solid Tumors (RECIST) 1.1, Prostate Cancer Working Group 2 (PCWG2) guidelines and days on trial (DOT) were recorded. All men were followed for 1 year or until progression. Four men had 18F-FDG-avid disease: two with widespread (DOT 53 and 76) and two with oligometastatic disease (DOT 231 and still on trial after 742+ days). Five men had non-18F-FDG-avid disease; three remained stable or improved (2 still on trial while one discontinued for non-oncologic reasons; DOT 225-563+), and 2 progressed (DOT 285 and 532). Despite the small sample size, Kaplan-Meier analysis showed a significant difference in progression free survival (PFS) between men with widespread 18F-FDG-avid, oligometastatic 18F-FDG-avid and non-18F-FDG-avid disease (p < 0.01). All men had 18F-NaF-avid disease. Neither 18F-NaF-avid disease extent nor intensity was predictive of treatment response. 18F-FDG-PET/CT may be superior to 18F-NaF-PET/CT and standard imaging in men with mCRPC on abiraterone and cabozantinib. 18F-FDG-PET/CT may have potential to stratify men into 3 groups (widespread vs. oligometastatic 18F-FDG-avid vs. non-18F-FDG-avid mCRPC) to tailor therapy. Further evaluation is warranted.
Zukotynski KA, Kim CK, Gerbaudo VH, Hainer J, Taplin ME, Kantoff P, den Abbeele AD, Seltzer S, Sweeney CJ. Are you the author?
Brigham and Women's Hospital, Harvard Medical School Boston, MA, USA; Dana-Farber Cancer Institute, Harvard Medical School Boston, MA, USA; Sunnybrook Health Sciences Centre, University of Toronto ON, Canada.
Reference: Am J Nucl Med Mol Imaging. 2014 Dec 15;5(1):72-82.