Background/AimWe prospectively investigated the potential usefulness of PET using a new tracer targeting integrin αvβ3 (termed RGD-K5) in patients with head and neck cancer (HNC) undergoing definitive concurrent chemoradiotherapy (CCRT).Patients and MethodsNewly diagnosed patients with locally advanced HNC scheduled for definitive CCRT were eligible. RDG-K5 PET and FDG PET scans were performed at three different time points (baseline, 2 weeks, and 3 months post-treatment).ResultsNine patients completed all of the three scans, whereas two patients withdrew after two scans only. Uptake of both RGD-K5 and FDG generally decreased following CCRT. However, the observed decrease did not differ significantly between complete responders and non-responders. At 3 months post-treatment, the uptake of both RGD-K5 and FDG at the main tumors was significantly lower in those who achieved complete responses than in those with residual tumors.ConclusionRGD-K5 PET has the potential to identify patients with incomplete responses to CCRT.