451P Utility of circulating free DNA 5’-end motif profile in the prediction of pathological response after neoadjuvant chemoradiotherapy in patients with locally advanced rectal cancer

For locally advanced rectal cancer (LARC) patients who achieved complete clinical response (cCR) after neoadjuvant chemoradiotherapy (nCRT), a “Watch & Wait” (W&W) approach is adopted to improve quality of life. However, W&W may increase the recurrence risk of those who are not pathological complete response (non-pCR). Cell-free DNA (cfDNA) end motifs have been used in cancer detection. But its utility in predicting pCR status has not been...