432 Background: Preoperative chemoradiotherapy (CRT) in rectal cancer reduces the local recurrence rate after operation and preserves the anus, but it is difficult to predict the effects of CRT. Our purpose of this study was to determine the effects and adverse events of CRT (S-1 or UFT) and to predict the response to CRT in rectal cancer by using both miRNA and DNA expression patterns. Methods: Rectal cancer patients (n=60) who underwent preoperative CRT were randomly divided into two groups (40Gy radiotherapy combined with S-1: 31 patients or UFT: 29 patients). The effects and adverse events of CRT were compared between S-1 group and UFT group. Additionally, RNA and DNA isolated from biopsy specimens of rectal cancer before preoperative CRT were hybridized to miRNA and DNA microarrays. Response to CRT was determined by histopathologic examination of surgically resected specimens. Results: Response to CRT determined by histopathologic examination of surgically resected specimens and RECIST were as follows: responders (grade 2 or 3) were 60%(S-1) and 52%(UFT) (p=0.52). Adverse events of CRT did not differ significantly between the 2 groups, and there was no adverse event of grade 3 or 4. As candidate predictive genes, 184 genes (S-1 group) and 193 genes (UFT group) were identified by DNA microarray, while 6 miRNA (S-1 group) and 16 miRNA (UFT group) were isolated by miRNA microarray as candidate predictive miRNA. Conclusions: Preoperative CRT using S-1 or UFT to rectal cancer is effective and the adverse events were acceptable. Expression profiling of both gene and miRNA may predict the effects of preoperative CRT, implicating the possible personalized therapy for patients with rectal cancer.
