Abstract
1372
Purpose: The aim of this study was to evaluate combined 18F-FDG-PET/CT imaging biomarkers during first line chemotherapy in patients with pancreatic ductal adenocarcinoma. Methods: This was a prospective, single-center, single-arm, open-label study (IRB12-000770). Patients were planned to undergo three 18F-FDG-PET/CTs, a baseline (PET1), early interim (PET2) and late interim (PET3) during first line chemotherapy. Established (mPERCIST / RECIST1.1) and maximally selected log-rank cut-offs for metabolic and radiographic tumor response assessment were applied. Patients were followed to collect data subsequent treatment and survival outcomes.
Results: The study population consisted of 29, 24 (83%), and 22 (76%) patients who underwent a PET1, PET2, and PET3, respectively. During a median follow up period of 14 months (maximum follow up, 58.3 months), 24 deaths occurred. Early metabolic responders, 7 / 24 patients (29%), and radiographic responders, 8 / 24 (33%), were defined as ≥ 20% decrease in SUVmax and ≥ 20% decrease in tumor size respectively. In early metabolic responders the median overall survival was 36.2 months (95%CI, 26.8-NYR, p=0.03) and in early radiographic responders was 23.4 months (95%CI, 19.6-NYR, p=0.23). Five / 21 patients were classified as dual-modality responders (late metabolic and size responders) while 7 patients were considered uni-modality responders (either metabolic or size responder). The median overall survival was not yet reached in dual-modality responders and 25.4 months (95%CI, 12.3-NYR) in uni-modality responders (p=0.108). Uni-modality responders trended toward improved survival (median overall survival 25.4 vs 10.5, p=0.09), while dual-modality responders showed significantly improved survival when compared with non-responders (median overall survival NYR vs 10.5, p=0.042). Conclusion: 18F-FDG PET/CT might potentially serve as a dual-modality interim imaging biomarker in patients with PDAC. Early metabolic response showed a significant survival improvement, however radiographic response was expectedly not evaluable at 4 weeks. Dual-modality response showed improved significantly improved survival compared to non-responders and moderately improved survival compared to uni-modality responders at 11 weeks.