18F-FDG PET/CT Imaging Biomarkers for Early and Late Evaluation of Response to First-Line Chemotherapy in Patients with Pancreatic Ductal Adenocarcinoma

The purpose of this study was to evaluate ¹⁸F-FDG PET/CT as an early and late interim imaging biomarker in patients with pancreatic ductal adenocarcinoma who undergo first-line systemic therapy. Methods: This was a prospective, single-center, single-arm, open-label study (IRB12-000770). Patient receiving first-line chemotherapy were planned to undergo baseline ¹⁸F-FDG PET/CT, early interim ¹⁸F-FDG PET/CT, and late interim ¹⁸F-FDG PET/CT. Cutoffs for metabolic and radiographic tumor response assessment as selected and established by receiver-operating-characteristic analysis were applied (modified PERCIST/RECIST1.1). Patients were followed to collect data on further treatments and overall survival. Results: The study population consisted of 28 patients who underwent baseline ¹⁸F-FDG PET/CT. Twenty-three of these (82%) underwent early interim ¹⁸F-FDG PET/CT, and 21 (75%) underwent late interim ¹⁸F-FDG PET/CT. Twenty-three deaths occurred during a median follow-up period of 14 mo (maximum follow-up, 58.3 mo). The median overall survival was 36.2 mo (95% CI, 28 mo to not yet reached [NYR]) in early metabolic responders (6/23 [26%], P = 0.016) and 25.4 mo (95% CI, 19.6 mo–NYR) in early radiographic responders (7/23 [30%], P = 0.16). The median overall survival was 27.4 mo (95% CI, 21.4 mo–NYR) in late metabolic responders (10/21 [48%], P = 0.058) and 58.2 mo (95% CI, 21.4 mo–NYR) in late radiographic responders (7/21 [33%], P = 0.008). Conclusion:¹⁸F-FDG PET may serve as an early interim imaging biomarker (at ∼4 wk) for evaluation of response to first-line chemotherapy in patients with pancreatic ductal adenocarcinoma. Radiographic changes might be sufficient for response evaluation after the completion of first-line chemotherapy.