A Review of Circulating Tumor DNA as a Biomarker Guide for Total Neoadjuvant Therapy in Patients with Locally Advanced Rectal Cancer

PURPOSE

Non-operative management of patients with locally advanced rectal cancer (LARC) is emerging as a popular approach for patients that have no evidence of disease following neoadjuvant therapy. However, high rates of local recurrence or distant metastases have highlighted the urgent need for robust biomarker strategies to aid clinical management of these patients.

METHODS

This review summarizes recent advances in the utility of cell-free (cf) and circulating tumor (ct) DNA as potential biomarkers to help guide individualized non-operative management strategies for LARC patients receiving neoadjuvant therapy.

RESULTS

Liquid biopsies and the detection of cfDNA/ctDNA is an emerging technology with the potential to provide a non-invasive approach to monitor disease response and improve the identification of patients with LARC that would best benefit from non-operative management.

CONCLUSIONS

Substantial work is still needed before cfDNA/ctDNA monitoring can be widely adopted in the clinical setting. Studies reviewed herein highlight several areas of opportunity for improving the effectiveness and utility of cfDNA/ctDNA for managing patients with LARC.

Can circulating tumor DNA be used for direct and early stage cancer detection?

In the August 16th issue of Science Translational Medicine, Phallen et al propose a method for early cancer diagnosis by using circulating tumor DNA (1). One major advance of this paper includes optimized sequencing of cell-free/circulating tumor DNA (ctDNA) without knowledge of tumor mutations. Evaluation of 200 patients with colorectal, breast, lung and ovarian cancer revealed mutations in ctDNA in approx. 60-70% of all patients, including stage 1 and stage 2 disease. If this data can be reproduced in asymptomatic individuals, they will likely have a major impact on early cancer detection and patient outcomes. In this commentary, we examine the feasibility of this approach for detecting small, asymptomatic tumors, based on previously published empirical data.