Novelties in treatment of locally advanced rectal cancer

Validation of microRNA-199b as A Promising Predictor of Outcome and Response to Neoadjuvant Treatment in Locally Advanced Rectal Cancer Patients

Simple Summary

The clinical management of locally advanced rectal cancer (LARC) patients would benefit for the establishment of molecular markers that could anticipate the response to neoadjuvant chemoradiotherapy (CRT). We aimed here to validate in an independent cohort our previous findings about the prognostic value showed by miR-199b in LARC as well as to explore its status in the disease progression. Notably, we confirmed in this work that miR-199b has a predictive value of both outcome and response to preoperative CRT in LARC patients further strengthen its potential usefulness in this disease.

Abstract

The absence of established predictive markers with value to anticipate response to neoadjuvant 5-fluorouracil (5-FU)-based chemoradiotherapy (CRT) represents a current major challenge in locally advanced rectal cancer (LARC). The tumor suppressor microRNA (miR)-199b has been reported to play a key role determining 5-FU sensitivity of colorectal cancer cells through the regulation of several signaling pathways, and has emerged as a novel molecular target to overcome the 5-FU resistant phenotype. Moreover, miR-199b downregulation was described as a common alteration that predicts lack of response to preoperative CRT in LARC but this issue needs to be confirmed in independent larger cohorts. Here, we evaluate the clinical impact of miR-199b in LARC and perform additional analyses to further clarify its potential relevance as novel marker in this disease. Thus, miR-199b expression was quantified by real-time-PCR in a cohort of 185 LARC patients, observing this miR downregulated in 22.2% of cases and significantly associated with higher tumor size (p = 0.026) and positive lymph node after CRT (p = 0.005), and higher pathological stage (p = 0.004). Notably, this alteration showed a strong independent predictive value of poor pathological response to neoadjuvant CRT (p = 0.004). Moreover, the subgroup of cases with low miR-199b levels had a markedly shorter overall (p < 001) and event-free survival (p < 0.001), and multivariate analyses showed that miR-199b deregulation represents an independent prognosticator for patient outcome in LARC. Interestingly, the prognostic impact of this miR was strongly significant in both younger and elderly patients, and was very effective determining patient recurrence (p = 0.004). Finally, we compared miR-199b expression profiles in a set of cases with pre and post-treatment samples available, observing that only a minimal response leads to miR-199b increase levels, further suggesting its potential clinical and therapeutic relevance as a promising marker and novel molecular target for the management of LARC.

MicroRNA-199b Downregulation Confers Resistance to 5-Fluorouracil Treatment and Predicts Poor Outcome and Response to Neoadjuvant Chemoradiotherapy in Locally Advanced Rectal Cancer Patients

Neoadjuvant 5-fluorouracil (5-FU)-based chemoradiotherapy followed by mesorectal excision is the current standard treatment in locally advanced rectal cancer (LARC) and the lack of complete response represents a major problem that compromises long-term patient survival. However, there is a lack of robust established markers predictive of response to this preoperative treatment available in the clinical routine. The tumor suppressor microRNA (miR)-199b directly targets the PP2A inhibitor SET, which has been involved in 5-FU resistance, and its downregulation has been found to correlate with poor outcome in metastatic colorectal cancer. Here, we studied the functional effects of miR-199b on 5-FU sensitivity after its ectopic modulation, and its expression was quantified by real-time-PCR in a cohort of 110 LARC patients to evaluate its potential clinical significance. Interestingly, our findings demonstrate that miR-199b enhances the sensitivity of colorectal cancer cells to 5-FU in a SET-dependent manner, and that both miR-199b overexpression and SET inhibition are able to overcome resistance to this drug using an acquired 5-FU-resistant model. MiR-199b was found downregulated in 26.4% of cases and was associated with positive lymph node levels after chemoradiotherapy (CRT, p = 0.007) and high pathological stage (p = 0.029). Moreover, miR-199b downregulation determined shorter overall (p = 0.003) and event-free survival (p = 0.005), and was an independent predictor of poor response to preoperative CRT (p = 0.004). In conclusion, our findings highlight the clinical impact of miR-199b downregulation predicting poor outcome and pathological response in LARC, and suggest the miR-199b/SET signaling axis as a novel molecular target to prevent the development of resistance to 5-FU treatment.

Retrospective review of total neoadjuvant therapy

BACKGROUND

Neoadjuvant chemoradiotherapy (nCRT) followed by resection and postoperative multi-agent chemotherapy (maChT) is the standard of care for locally advanced rectal cancer. Using this approach, maChT administration can be delayed for several months, leading to concern for distant metastases. To counteract this, a novel treatment approach known as total neoadjuvant therapy (TNT) has gained popularity, in which patients receive both maChT and nCRT prior to resection. We utilized the National Cancer Database to examine temporal trends in TNT usage, and any potential effect on survival.

AIM

To study the temporal trends in the usage of TNT and evaluate its efficacy compared to neoadjuvant chemoradiation.

METHODS

We queried the National Cancer Database for patients with locally advanced rectal cancer, Stage II-III, from 2004-2015 treated with nCRT or TNT. TNT was defined as maChT initiated ≥ 90 d prior to nCRT initiation. Overall survival was calculated from the date of diagnosis to the date of last contact or death using Kaplan-Meier curves to present the cumulative probability of survival, with log-rank statistics to assess significance. Multivariable cox regression was used to identify predictors of survival and propensity score analysis accounted for bias.

RESULTS

We identified 9066 eligible patients, with 8812 and 254 patients receiving neoadjuvant chemoradiation followed by maChT and TNT, respectively. Nodal involvement, stage III disease, and treatment in recent years were predictive of TNT use. There was greater use of TNT with more advanced stage, specifically > 1 node involved (odds ratio [OR] = 2.88, 95% confidence interval [CI]: 2.11-3.93, P < 0.01) and stage III disease (OR = 2.88, 95%CI: 2.11-3.93, P < 0.01). From 2010 to 2012 the use of TNT increased (OR = 2.41, 95%CI: 1.27-4.56, P < 0.01) with a greater increase from 2013 to 2015 (OR = 6.62, 95%CI: 3.57-12.25, P < 0.01). Both the TNT and neoadjuvant chemoradiation arms had a similar 5-year survival at 76% and 78% respectively. Multivariable analysis with propensity score demonstrated that increased age, high comorbidity score, higher grade, African American race, and female gender had worse overall survival.

CONCLUSION

Our data demonstrates a rising trend in TNT use, particularly in patients with worse disease. Patients treated with TNT and nCRT had similar survival. Randomized trials evaluating TNT are underway.

Translational Potential of MicroRNAs for Preoperative Staging and Prediction of Chemoradiotherapy Response in Rectal Cancer

Colorectal cancer is the third most common cancer and the second cause of cancer-related deaths. Rectal cancer presents roughly one-third of all colorectal cancer cases and differs from it on both anatomical and molecular levels. While standard treatment of colon cancer patients is radical surgery, rectal cancer is usually treated with pre-operative chemoradiotherapy followed by total mesorectal excision, which requires precise estimation of TNM staging. Unfortunately, stage evaluation is based solely on imaging modalities, and they often do not correlate with postoperative pathological findings. Moreover, approximately half of rectal cancer patients do not respond to such pre-operative therapy, so they are exposed to its toxic effects without any clinical benefit. Thus, biomarkers that could precisely predict pre-operative TNM staging, and especially response to therapy, would significantly advance rectal cancer treatment—but till now, no such biomarker has been identified. In cancer research, microRNAs are emerging biomarkers due to their connection with carcinogenesis and exceptional stability. Circulating miRNAs are promising non-invasive biomarkers that could allow monitoring of a patient throughout the whole therapeutic process. This mini-review aims to summarize the current knowledge on miRNAs and circulating miRNAs involved in the prediction of response to treatment and pre-operative staging in rectal cancer patients.