Abstract 400P
Background
Neoadjuvant chemoradiotherapy (NCRT) has been consolidated as the main strategy for the treatment of locally advanced rectal cancer (LARC).However, heterogeneous responses are observed, with only about 15-20% of patients presenting a complete pathological response (pCR).Thus, countless studies evaluate possible biomarkers capable of predicting pCR and more intense neoadjuvant treatments to increase these rates. The objective of this prospective study was to analyze whether the protein expression of RAD23 homolog B (RAD23B) in the circulating tumor cells (CTCs) (at baseline-C1) could correlate with the response to NCRT.
Methods
Between 2016 and 2020, 63 patients (pts) with LARC who underwent NCRT followed by radical surgery, were included in the study. Blood samples were collected before the beginning of NCRT (C1) and the evaluation of RAD23B protein expression in CTCs was correlated with the anatomopathological examination of response of patients undergoing surgery (n:56). CTCs were isolated and quantified by ISET®. RAD23B protein was analyzed by immunocytochemistry and visualized by bright field microscopy.
Results
The mean age was 56 years old (34-92). Among the pts analyzed, 34 (54%) carried tumors at the distal rectum, 57 (90%) had clinical tumor stage (cT) T3/T4, 58 (92%) clinical nodal (cN) positive and 32 (52%) had preoperative carcinoembryonic antigen (CEA) >3 ng/mL Thirteen (23,2%) patients had pCR with NCRT. RAD23B expression in CTCs was present in 54% of non-responders, while in pCR group, it was absent in the majority of pts (91.7%; p=0.019). In multivariate logistic regression models for pCR, including CEA, gender, cT and RAD23B expression in CTCs, the latter was an important independent prognostic factor [Odds Ratio (OR) 0.064; 95% confidence interval (CI): 0.006 – 0.751; p=0.029].
Conclusions
This prospective study demonstrated the correlation between the absence of expression of RAD23B in CTCs (C1) and pCR, being an important result for future clinical studies. This analysis may identify NCRT responders candidates, helping to choose the best therapeutic approach for each individual.
Clinical trial identification
NCT: 02979470.
Editorial acknowledgement
Legal entity responsible for the study
The authors.
Funding
Funding was received from the Public Ministry of Brazil (TAC-MP- PAJ No. 000968.2012.10.000 / 0) and the National Institute for Science and Technology in Oncogenomics and Therapeutic In-novation (INCT FAPESP / CNPq 2014 / 50943-1).
Disclosure
All authors have declared no conflicts of interest.