RRM2 and cancer: Univariate analysis revealed that the patients with cancer tissues exhibiting positive RRM2 immunoreactivity had poorer survival than those with cancer tissues exhibiting negative RRM2 immunoreactivity [5-year survival rate: 76.4 vs. 95.5%; hazard ratio (HR): 7.94, 95% confidence interval (CI): 1.07–58.82; p = 0.016] (Table 2).