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

<p>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 (TMR<sub>ATSM</sub> and TMR<sub>FDG</sub>). TMR<sub>ATSM</sub>, one of the intensity-based redox parameters, showed a significant difference in PFS between two groups (<i>p</i> = 0.03), whereas TMR<sub>FDG</sub>, one of the intensity-based metabolic parameters, did not (<i>p</i> = 0.15). The three-year PFS rate was 74% for patients with lower accumulation tumors (TMR<sub>ATSM</sub> ≤ 3.2) and 29% for those with over-reductive tumors (TMR<sub>ATSM</sub> > 3.2).</p>