CEACAM5 and colorectal carcinoma: R2 and p-values of the difference in serum levels of modified circulating cell-free nucleosomes and carcinoembryonic antigen (CEA) between individuals with stage I–IV colorectal cancer (CRC), between individuals with comorbidity (cardiovascular disease, diabetes I/II, lung disease and rheumatic disease) and healthy individuals, and between gender and age in healthy individuals