GEMCAD-REVEAL STUDY - Circulating Tumor DNA as a Predictor of Relapse in Patients With Locally Advanced Rectal Cancer.

The evaluation of the tumor response to chemoradiotherapy/total neoadjuvant therapy (CRT/TNT) remains a challenge. The integration of a blood-based biomarker such as ctDNA with clinico-radiological tools could offer the potential advantage of improving accuracy of assessment of tumor response to neoadjuvant therapy. Furthermore, data on functional outcomes and quality of life after total mesorectal excision (TME) and especially after " Watch And Wait" (WW) is scarce.

REVEAL is a prospective, multicenter study in which the response to TNT in correlation with liquid biopsy (LB) of patients with rectal cancer in Spain will be evaluated. It is planned to include 120 patients. All patients will be aged 18 years or older, with histologically confirmed rectal adenocarcinoma, located in the mid or distal third (with the inferior margin within 12cm from the anal verge), clinically staged II and III (cT3-T4 and/or any TN+), scheduled to undergo TNT will be eligible. All cases and treatment decisions will be discussed by local Multidisciplinary Boards. Patients will be included consecutively when visiting the corresponding health centers for outpatient visits or hospitalization.

The objective of the present study is to evaluate the role of ctDNA in the prediction of relapse in patients diagnosed with locally advanced rectal cancer (LARC) treated with TNT followed by WW or TME based on a clinical assessment of the local response.

HYPOTHESIS ctDNA is a predictor of complete clinical response and could potentially be used to guide patient selection for WW strategy.

ctDNA is an early marker of local tumor relapse and could potentially guide strategy changes during follow-up.

Patients who are enrolled in a WW strategy have better long-term functional outcomes in comparison to patients who undergo surgery.

OBJECTIVES

PRIMARY:

To estimate the positive predictive value (PPV) and the negative predictive value (NPV) of the post-TNT ctDNA measurement to identify relapse (local or distant) in the 2 years after TNT.

SECONDARY:

Secondary objectives related to ctDNA and tumor response to TNT:

• To estimate the concordance between the post-TNT ctDNA measurement and the clinical evaluation of response (endoscopy-biopsy, DRE and MRI) to TNT.

• To estimate the concordance between the ctDNA measured after TNT and the endoscopy-biopsy evaluation of response.

• To estimate the concordance between the ctDNA measured after TNT and the MRI-defined response pattern groups.

Secondary objectives related to ctDNA measure during follow-up and relapse:

• To estimate the positive predictive value and the negative predictive value of ctDNA measured during the follow-up after TNT to identify relapse (local or distant) in the 2 years after TNT.

• To estimate the positive predictive value and the negative predictive value of ctDNA measured during the follow-up after TNT to identify local relapse in the 2 years after TNT

• To estimate the positive predictive value and the negative predictive value of ctDNA measured during the follow-up after TNT to identify distant relapse in the 2 years after TNT

Secondary objective related to functional impact of TME and WW:

-To describe anorectal, urinary and sexual function in the TME and WW groups.

Secondary objective related to ctDNA and survival:

-To assess the association of ctDNA levels (at baseline, post-treatment and during follow-up) with the survival outcomes (overall and disease-free survival, locoregional and distant recurrence, together with the pattern of recurrence).