Liquid Biopsy in Rectal Cancer: Applications in Neoadjuvant Therapy Monitoring

Abstract

Introduction: Currently, regarding locally-advanced rectal cancer, a complete pathological response after neoadjuvant therapy is poorly predicted by conventional imaging modalities. Methods of response assessment are now starting to have a pivotal role in improving treatment strategies. However, the clinical potential of ctDNA analysis in non-metastatic rectal cancer remains unsettled. Thus, this work aims to review the established evidence on the role of liquid biopsies as a method of assessing the response to neoadjuvant therapy and refining the current treatment strategies of locally-advanced rectal tumors. Methods: A literature search was conducted in the MEDLINE database, using PubMed search engine, the Web of Science and Scopus databases. A total of 45 articles were comprised in this literature review. Results/Discussion: The results evidenced in this work suggest that, although no predictive molecular biomarker for response to nCRT has been proved to be sufficiently robust to have clinical utility on its own, significant differences between response and nonresponse could be found during treatment. Biomarkers such as DNA level variations, DNA integrity index, methylation or mutation status of specific genes, in the context of a multidisciplinary approach to treatment, have proven to be a valuable tool in assessing treatment response and refining therapy strategies. Conclusion: The inclusion of liquid biopsies in the monitorization of neoadjuvant treatment response can improve the accuracy of the clinical and radiological assessment of rectal cancer patients and offer, in the near future, a concrete opportunity for a more personalized treatment approach.