Liquid Biopsy Assay Predicts Lymph Node Metastases in T1 Colorectal Cancer

When patients have T1 colorectal cancer (CRC) resected, histologic features, such as deep submucosal invasion, poor differentiation, lymphovascular invasion, and high-grade tumor budding, are used to select patients needing adjuvant surgical therapy. 

A liquid biopsy assay was developed based on 4 micro RNAs and 5 messenger RNAs. To evaluate the assay, researchers used a training cohort consisting of 46 T1 CRC serum samples and a validation cohort with 142 CRC serum samples. Of these samples, 5 in the training cohort and 12 in the validation cohort were positive for lymph node metastasis (LNM). The assay alone identified LNM with an area under the curve (AUC) of 0.86. It also had a sensitivity of 80%, specificity of 92.7%, a positive predictive value of 57%, and a negative predictive value of 97%. When clinical risk factors were added to the model, the AUC rose to 0.90. 

Given that all the subjects were at high risk for metastases based on clinical factors, overtreatment (unnecessary surgical resection) occurred in 92% of patients when just clinical factors were used to determine the need for further treatment. However, the assay alone resulted in overtreatment of only 22% of patients, and the risk stratification model with the assay plus clinical risk factors resulted in overtreatment of 18%.