A Pilot, Prospective, Observational Study to Investigate the Value of NGS in Liquid Biopsies to Predict Tumor Response After Neoadjuvant Chemo-Radiotherapy in Patients With Locally Advanced Rectal Cancer: The LiBReCa Study

Abstract

IntroductionCirculating tumor DNA (ctDNA) correlates with the response to therapy in different types of cancer. However, in patients with locally advanced rectal cancer (LARC), little is known about how ctDNA levels change with neoadjuvant chemoradiation (Na-ChRT) and how they correlate with treatment response. This work aimed to explore the value of serial liquid biopsies in monitoring response after Na-ChRT with the hypothesis that this could become a reliable biomarker to identify patients with a complete response, candidates for non-operative management.Materials and MethodsTwenty-five consecutive LARC patients undergoing long-term Na-ChRT therapy were included. Applying next-generation sequencing (NGS), we characterized DNA extracted from formalin-fixed paraffin embedded diagnostic biopsy and resection tissue and plasma ctDNA collected at the following time points: the first and last days of radiotherapy (T0, Tend), at 4 (T4), 7 (T7) weeks after radiotherapy, on the day of surgery (Top), and 3–7 days after surgery (Tpost-op). On the day of surgery, a mesenteric vein sample was also collected (TIMV). The relationship between the ctDNA at those time-points and the tumor regression grade (TRG) of the surgical specimen was statistically explored.ResultsWe found no association between the disappearance of ctDNA mutations in plasma samples and pathological complete response (TRG1) as ctDNA was undetectable in the majority of patients from Tend on. However, we observed that the poor (TRG 4) response to Na-ChRT was significantly associated with a positive liquid biopsy at the Top.ConclusionsctDNA evaluation by NGS technology may identify LARC patients with poor response to Na-ChRT. In contrast, this technique does not seem useful for identifying patients prone to developing a complete response.

Circulating tumour DNA as biomarker for rectal cancer: A systematic review and meta-analyses

“…Therefore, in recent years, more and more studies utilising techniques that can specifically detect ctDNA have increasingly been described ( 22 , 25 , 28 – 35 ). The largest study conducted so far by Tie et al., including 159 patients with LARC, has demonstrated that ctDNA status could be used to classify groups as very high and low risk for recurrence ( 25 ).…”

Treatment stratification and prognosis assessment using circulating tumor DNA in locally advanced rectal cancer: A systematic review and meta‐analysis

“…A total of 11 studies were pooled to analyze ctDNA prediction of pCR in Figure 1 28,29,31–39 . ctDNA‐negative patients were more likely to have a pCR during LARC treatment (RR = 1.64 95% CI: 1.26–2.12, p < 0.05).…”

“…ctDNA‐negative patients were more likely to have a pCR during LARC treatment (RR = 1.64 95% CI: 1.26–2.12, p < 0.05). In the subgroup analysis, baseline included 10 studies, and ctDNA did not predict pCR (RR = 1.19, 95% CI: 0.87–1.61, p > 0.05) 28,29,31–38 . On‐CRT included four studies, and ctDNA‐negative patients were more prone to pCR (RR = 2.67, 95% CI: 1.05–6.78, p < 0.05) 28,32,34,35 .…”

“…A number of studies have explored the role of ctDNA in predicting pCR, tumor recurrence risk, and prognosis in LARC. However, the evidence is still insufficient for direct clinical application due to the small sample size and the different experimental approaches 28–39 . In addition, published studies on the role of ctDNA in LARC have shown inconsistent results.…”

Evaluation of ctDNA in the Prediction of Response to Neoadjuvant Therapy and Prognosis in Locally Advanced Rectal Cancer Patients: A Prospective Study

“…Unlike Pazdirek et al [ 40 ] and Wang et al [ 33 ], in which ctDNA was strongly eliminated from plasma from baseline to post-treatment samples (probably due to tumor shrinkage and less ctDNA available from enzymatic digestion induced by radiation damage [ 44 ]), in our study we observed that some mutations appeared in the post-treatment sample that were not present initially, although the MAF did not change significantly and could not predict outcomes. This was probably related to the low number of post-treatment analyses or the limited sensitivity of NGS for identifying pCR, as reported by Roesel et al [ 45 ].…”