The Predictive Role of microRNA 142–5p, microRNA 182–3p, and microRNA 99a-3p in Disease-Free Survival and Overall Survival in Patients with Locally Advanced Rectal Cancer After Neoadjuvant Chemoradiation Therapy and Radical Surgery

Background/Objectives: MicroRNAs (miRNAs) are likely to play a significant role in the prediction of rectal cancer response to chemoradiation therapy, offering insights that complement other biological tumour markers. The study aimed to perform miRNA profiling in rectal cancer tissues in patients with good (GR) and bad response (BR) to neoadjuvant chemoradiation therapy (nCRT), select the potentially clinically relevant ones, and further evaluate their relationship with subsequent disease outcomes and survival prognosis. Methods: A total of 40 selected patients with locally advanced rectal cancer who received nCRT and following surgical treatment in the period from 2016 to 2021 were involved. Two study groups were created – GR and BR according to the Dworak tumour regression grading (TRG) system. The identification of 752 miRNAs was conducted in rectal cancer tissue. Results: Six upregulated miRNAs were set as clinically significant within the selected samples and subsequently validated in the BR and GR groups. MiR-142-5p, miR-182-3p, and miR-99a-3p exhibited statistical significance in validation. The results showed that BR to nCRT, lower expression of miRNA-142-5p and miR-99a-3p, and higher expression of miR-182-3p were associated with a trend toward worse local recurrence-free survival, distant metastases-free survival, and overall survival in comparison to GR. Conclusion: MiRNAs may potentially serve as clinical biomarkers in prediction of disease-free survival and overall survival in patients with rectal cancer.