Kaplan-Meier curves of progression-free survival (PFS) for 62Cu-ATSM PET (a) and 18F-FDG PET (b) in patients with HNC.

Two groups of high (dotted lines) and low (solid lines) tracer accumulation were determined by each cut-off value of the tumor-to-muscle ratios (TMRATSM and TMRFDG). TMRATSM, one of the intensity-based redox parameters, showed a significant difference in PFS between two groups (p = 0.03), whereas TMRFDG, one of the intensity-based metabolic parameters, did not (p = 0.15). The three-year PFS rate was 74% for patients with lower accumulation tumors (TMRATSM ≤ 3.2) and 29% for those with over-reductive tumors (TMRATSM > 3.2).