The mean catalase activity of people with a chronic cancer diagnosis (176.47 U/mg Hb) was significantly lower than the corresponding catalase activity of people with a recent cancer diagnosis (206.64 U/mg Hb, p = 0.024) and with a recent (215.44 U/mg Hb, p < 0.001) and chronic non-cancerous lesions (209.34 U/mg Hb, p < 0.001). Here, GSTM1 is linked to cancer.