Blood levels of ROS, GPx, and SOD in 95 control subjects and 91 patients with epithelial ovarian cancer according to stage. ROS levels were significantly higher (P < .001), while GPx and SOD activities were significantly lower in patients with cancer than in control subjects (P < .001). P was calculated by 2-sided Student t test. The box plots in the figure represent columns of data as boxes whose extents indicate the 25th and 75th percentiles of the column. The line inside the box represents the median. + marks the value of the mean. Capped bars indicate the minimum and maximum value observed.