The early and accurate detection of CRLM is of great significance for the treatment and prognosis of colorectal cancer patients. However, due to the lack of specific symptoms and the limited detection methods, CRLM often entails a missed diagnosis, with the disease entering the later stages when obvious symptoms appear [8, 9]. Previous studies have demonstrated that upon diagnosis, approximately 80% of CRLM patients have lost the opportunity to eliminate the metastasis via surgery and are often left with a survival rate of only a few months. However, the 5-year survival rate of CRLM patients can reach up to 40% if the liver metastasis is completely eliminated through surgery . At present, the common CRLM imaging detection methods include CT, ultrasound and enhanced MRI examinations. An enhanced MRI has the advantages of presenting an enhancement of the lesions, being more sensitive to small lesions and being able to detect liver metastasis early. The technique also evaluates the residual volume of the liver, which provides a reference for surgical planning and improves the success rate of the surgery .
CEA is one of the first and most widely used tumour markers. It is a specific acidic glycoprotein of a human embryonic antigen. Studies have found that the CEA expression level and distant metastasis of colorectal cancer have a certain correlation when CEA > 15ng/mL of colorectal cancer patients with postoperative distant metastasis probability is high , but the false positive and false negative situation is more. CA19-9 is a related antigen secreted by digestive system tumour cells, which is highly expressed in gastric, colon, rectal and pancreatic cancer tissues. Studies have shown that CEA, CA19-9 and CA125 are significant in predicting liver metastasis of colorectal cancer. Among them, CEA is significant in predicting the T stage, CA19-9 is significant in predicting the T and N stages and CA125 is significant in predicting the degree of differentiation of the primary tumour.
In the present research, the results of the enhanced MRI examination and clinicopathological examination for liver metastasis in patients with colon cancer were found to be consistent (Kappa coefficient = 0.788, P < 0.000). However, the two methods demonstrated some inconsistencies. The sensitivity and specificity of the enhanced MRI examination were 94.0% and 84.7%, respectively, which indicated that given the 1.8 million new cases of colon cancer reported each year, many people could be misdiagnosed or have a missed diagnosis when using an MRI examination alone. To improve the outcome for CRLM patients, other detection methods could be combined with an MRI examination to improve the sensitivity and/or specificity.
In the occurrence and progression of colorectal cancer, the tumour markers will change due to the expression and accumulation of multiple genes. Serological tumour markers have the advantages of a fast diagnosis and small trauma diagnosis. A study on the relationship between serological indexes and pathological parameters in 279 patients with colorectal cancer found that the sensitivity of CEA, CA19-9, CA72-4 and CA125 to colon cancer was in the top five of the serum blood indexes studied and was associated with pathological tumour lymph node metastasis and vascular invasion. This indicates that it may be related to the liver metastasis of colon cancer. However, there is no consensus on the diagnostic criteria for CRLM patients in terms of the above indicators [12, 13].
In the present study, the highest specificity (94.61%), positive predictive value (92.68%) and positive likelihood ratio (12.67%) were obtained with an MRI examination combined with a serial CEA. However, this method could exclude colon cancer patients without liver metastasis. The combination of an MRI and parallel CEA had the highest sensitivity (98.80%) and negative predictive value (97.22%) but the lowest negative likelihood ratio (0.03), which means that this combination could improve the referral rate of CRLM patients.
CEA is produced by the digestive tract. The expression level of CEA is extremely low in healthy individuals but is significantly increased when a digestive tract tumour occurs . As such, CEA is a relatively broad-spectrum tumour marker, with its expression increased in liver, colon and gastric cancer patients. The antigen can easily appear on the surface of cancer cells; is captured by Kupffer cell-specific receptors in the liver; can induce the expression of IL-1α, IL-1β and other cytokines, as well as specific cancer-cell adhesion factors; and can promote the retention of cancer cells in the capillary network and liver metastasis . The CEA expression level in the serum of CRLM patients will be significantly increased, and previous studies have found that CEA levels are associated with the prognosis of patients with colon cancer metastasis . Since the 5-year survival rate after early surgical resection of CRLM lesions is generally greatly improved, the recommendation is to use the method of enhanced MRI combined with CEA to provide a reference for the early diagnosis of liver metastasis in patients with colon cancer and evaluate the surgical feasibility of patients in a timely manner.
As this study only included the patients from one hospital as the research subject, some admission rate bias could have been introduced. Furthermore, no other imaging detection method was designed in the experimental scheme, which was not conducive to a more objective evaluation of the diagnostic value of an MRI examination combined with serological indexes. Therefore, multi-centre clinical trials must be carried out in the future, with a variety of methods used as controls to further evaluate the diagnostic value of an MRI examination combined with serological indicators for CRLM.