Rectal cancer response to neoadjuvant chemoradiotherapy (pCRT) is highly variable. In fact, it has been estimated that only about 21 % of patients show pathologic complete response (pCR) after therapy, while in the most of the patients a partial or incomplete tumour regression are observed. Consequently, patients with a priori chemoradioresistant tumour should not receive the treatment, which is associated with substantial adverse effects and does not guarantee any clinical benefit. Despite for locally advanced rectal cancer patients (LARC) a standardized neoadjuvant treatment protocol is applied, the identification and the usefulness of prognostic or predictive biomarkers can improve the antitumoural treatment strategy, modifying the sequence, dose and combination of radiotherapy, chemotherapy and surgical resection.
For these reasons, a growing number of studies are actually focussed on the discovery and the investigation of new predictive biomarkers of response to pCRT. In this review, we have selected the most recent literature (2012-2017) regarding the employment of blood-based biomarkers potentially predicting pCR in LARC patients and we have critically discussed them to highlight their real clinical benefit and the current limitations of the proposed methodological approaches..