Characteristics of tumour markers CEA, CA 50 and CA 242 in serum with reference to colorectal cancer

Abstract: There is no consensus on if and how to conduct colorectal cancer surveillance. Serum levels of tumour markers and especially CEA increase before a recurrence is detected by clinical diagnosis. Second look surgery based on elevated serum levels of CEA has been beneficial for individual patients. Due to inconsistent findings, CEA-measurements after curative surgery hold a low grade of recommendation.The aim of the present study was to identify better surveillance tools using tumour markers for indicating relapsing colorectal cancer. Standard levels and fluctuation in cancer-free individuals in an age group where cancers are likely to occur were unknown, as was the influence of surgery in cancer-free patients undergoing surgery for benign disease and in patients surviving colorectal cancer. The aim was to establish those serum levels of CEA, CA 50 and CA 242. Based on these findings, individual cut-off levels of markers were to be identified. Also levels of CEA and CA 242 in future cancer patients were to be measured.It was found that the 90th percentile (chosen as standard level) of serum levels of CEA, CA 50 and CA 242 were 5,6 ng/ml, U/ml and 25 U/ml respectively. Serum-levels of CEA were higher in smokers and also increased with age. The fluctuation was below 20% for all markers. There was a transient decline in serum levels of CEA after surgery and they had not recovered until one year after the surgical procedure. Patients surviving colorectal cancer had a similar decline. In the post-operative period there was a positive relation between CEA levels and an inverse relation between CA 242 levels and Dukes´ staging in the patients surviving colorectal cancer. With individual cut-off levels all hepatic metastases occurring during the test period (two years after surgery) were indicated by CEA (0-19) months before they were clinically detected. In total twenty-four recurrences were detected during the test period. Twenty-one (88%) were indicated by CEA, eleven by CA 50 (46%) and nineteen (79%) by CA 242 (individual cut-off). Serum levels of CEA and CA 242 were highest close to cancer diagnosis