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

The standard treatment for locally advanced rectal cancer (T3 -T4 and / or N+) is neoadjuvant (pre-operative) chemo-radiotherapy (nCRT) followed by radical surgery. In patients after complete response following nCRT, surgery may not add any survival benefit but it is still performed.

Since clinical complete response has only partial concordance with pathological complete response, an additional method that helps identify those patients with a true complete response is needed to avoid unnecessary surgery and its associated potential complications..

The hypothesis underlying this study is that the quantitative and qualitative evaluation of circulating tumor DNA (ctDNA) of liquid biopsy, based on the amount of ctDNA or on the detection of specific gene alterations respectively, may be directly correlated to the clinical, histopathological and radiological response of the tumor to nCRT.

This study will not interfere with the patient's routine treatment pathway and there will be no deviation from the standard of care. The only additional study intervention will be the collection of blood samples at 6 different time points which can be combined with the regular blood examination performed during the treatment.

At the time of diagnosis, tumor staging and histopathology on tumor biopsy will be performed. Patients will receive standardized neoadjuvant therapy and will be operated after an observational period of 10 weeks. Peripheral blood sample will be collected at 6 time points: pre-nCRT, at the end of the nCRT, at 4th and 7th week post-CRT, on the day of the surgery (before surgical resection), on the post-operative day 5 (in hospital). Mesenteric blood sample will be collected intra-operatively on the day of the surgery. Tumor sampling will be performed during tumor staging, as standard of care, and on the resection specimen. A combined qualitative and quantitative approach for the molecular characterization of tissue and liquid biopsy using next-generation sequencing will be carried out.