Circulating cell-free DNA as predictor of pathological complete response in locally advanced rectal cancer patients undergoing preoperative chemoradiotherapy

Christina Glismand Truelsen; Camilla Skovhus Kronborg; Brita Singers Sørensen; Louise Bach Callesen; Karen-Lise Garm Spindler

doi:10.1016/j.ctro.2022.06.002

Circulating cell-free DNA as predictor of pathological complete response in locally advanced rectal cancer patients undergoing preoperative chemoradiotherapy

Clin Transl Radiat Oncol. 2022 Jun 8:36:9-15. doi: 10.1016/j.ctro.2022.06.002. eCollection 2022 Sep.

Authors

Christina Glismand Truelsen^{1

2}, Camilla Skovhus Kronborg², Brita Singers Sørensen², Louise Bach Callesen¹, Karen-Lise Garm Spindler^{1

3}

Affiliations

¹ Department of Experimental Clinical Oncology, Arhus University Hospital, Denmark.
² Danish Centre for Particle Therapy, Aarhus University Hospital, Denmark.
³ Department of Oncology, Aarhus University Hospital, Denmark.

Abstract

Background: The watch and wait (W&W) strategy is proposed for patients with locally advanced rectal cancer (LARC) achieving clinical complete response (cCR) after neoadjuvant radiotherapy. cCR is only in partial concordance with pathological complete response (pCR) due to persisting viable tumour cells. The aim was to investigate circulating-free-deoxyribonucleic-acid (cfDNA) as a biomarker for prediction of pCR.

Materials and methods: Patients treated with neoadjuvant radiotherapy for LARC, were included in a prospective biomarker study in Aarhus, Denmark from 2017 to 2020. Plasma cfDNA levels were analysed by a direct fluorescent assay (DFA). Surgical specimens were reviewed by pathologists to categorize response to cytotoxic therapy.

Results: In total, 76 patients were included with plasma available at baseline (n = 70), mid therapy (n = 50), and end of therapy (n = 54). Higher cfDNA levels were observed in LARC patients compared with healthy subjects (p < 0.01). By ROC analysis (AUC: 0.87 (95% CI, 0.81-0.92)) the optimal cut-off was 0.71 ng/µL for differentiation between healthy subjects and LARC patients. Thirteen patients obtained pCR with a median cfDNA level of 0.57 ng/µL at end of therapy. Patients with cfDNA levels at end of therapy below the cut-off (p < 0.02) and 'cfDNA responders' with descending levels greater than the 75th percentile during therapy had a significantly higher chance of pCR (p < 0.01).

Conclusion: This hypothesis generating study indicates that low cfDNA levels at end of treatment or ´cfDNA responderś might be associated with pCR. Quantification of cfDNA by the rapid and feasible DFA analysis could potentially facilitate personalized follow-up as a complementary tool to identify candidates for a W&W strategy.

Keywords: CRT, chemoradiotherapy; DFA, direct fluorescent assay; IMRT, intensity modulated radiotherapy; LARC, locally advanced rectal cancer; NGS, next generation sequencing; RT, radiotherapy; VMAT, volumetric modulated arc therapy; W&W, watch and wait; cCR, clinical complete response; cfDNA, circulating cell free deoxyribonucleic acid; ddPCR, digital droplet polymerase chain reaction; ng/µL, nanogram per microliter.; pCR, pathological complete response; qPCR, quantitative polymerase chain reaction.