LincRNA-p21 as predictive response marker for preoperative chemoradiotherapy in rectal cancer.

Abstract

e15534 Background: Preoperative chemoradiotherapy (CRT) is a standard treatment for locally advanced rectal cancer (RC) patients (pts). Despite the benefits of CRT, its use in non-responder pts can be associated with increased toxicities and resection delay. The identification of CRT response biomarkers, such as long non-coding RNAs (lncRNA), could improve the management of these pts. LincRNA-p21 is a lncRNA involved in the p53 pathway and angiogenesis regulation that acts as prognostic marker in several tumors. We aim to study lincRNA-p21 expression in pretreatment samples from RC pts treated with CRT to evaluate whether lincRNA-p21 can act as a predictive biomarker for CRT response. Methods: RNA from pretreatment endoscopy biopsies from 58 RC pts treated with preoperative CRT at Mutua Terrassa University Hospital were analyzed. Pathological response was classified according to the tumor regression grade (TRG) Dworak classification. LincRNA-p21 expression was determined by RTqPCR and was correlated with CRT response and, time to relapse (TTR), disease-free survival (DFS) and overall survival (OS). Results: Samples from 58 pts were analyzed. Most of them males (n = 40, 69%). Median age at diagnosis of 67 (44-82) years. Fifty (86.2%) pts reported stage III and, 42 (72.4%) pts assessed TRG 0-3 with a 70.7% of downstaging reported. LincRNA-p21 was upregulated in stage III tumors (p < 0.0001) and also in tumors with worst response to CRT regarding TRG, TGR0-3 (TRG0-3, n = 42 vs TRG4, n = 16, p = 0.019). In this line, the ROC curve analysis showed that lincRNA-p21 expression had capacity to distinguish pts with maximum response (TRG4) from others (AUC:0.7; p = 0.02). The binary logistic regression analysis validated its independence as response biomarker. LincRNA-p21 levels correlated with pts relapse after surgery. When the pts were classified in 3 groups, high, medium and low, according to lincRNA-p21 levels, RC pts with highest lincRNA-p21 expression had the shortest TTR. TTR for pts with high levels was 74.5 months (m) (95% CI:31-117), while it was 114 m (95% CI:95-133) for those with Medium levels and 123 m (95% CI:111-134) for those with low levels (p = 0.047). Conclusions: LincRNA-p21 is a marker of advanced disease and worse response to CRT. LincRNA-p21 may add valuable information for individualizing pre-operative CRT in locally advanced RC pts.