GSTM1 and colorectal cancer: In fact the prevalence of colorectal cancer in the non-returners within this study (3.8%) is comparable with the reported prevalence in the literature of symptomatic patients who return FIT tests with results between 20–49 μg Hb/g (3.6%)10 and 10–99.9 μg Hb/g (3.8%)6.