title: Metformin enhances the response to radiotherapy in diabetic patients with rectal cancer.
abstract: OBJECTIVE
  Metformin may have anticancer effects and could improve response to radiotherapy in several malignancies. We aimed to investigate the effect of metformin on response to radiotherapy in rectal cancer.
  
  
  METHODS
  A total of 543 rectal cancer patients who were treated with neoadjuvant chemoradiotherapy followed by radical surgery from January 2007 to December 2011 were reviewed. Patients were divided into three groups: diabetics taking metformin (n = 42), diabetics not taking metformin (n = 29), and non-diabetics (n = 472). Tumor response and survival were compared between groups.
  
  
  RESULTS
  The rates of N downstaging and tumor regression grades (TRG) 3-4 were significantly higher in diabetics taking metformin (p = 0.006 and p = 0.029, respectively). There were no significant differences between groups in terms of T downstaging and pathologic complete response. On multivariate analysis, metformin use was associated with increased rates of N downstaging and TRG 3-4 (p = 0.003 and p = 0.019, respectively). Recurrence-free survival, disease-free survival, and overall survival rates were not significantly different between groups.
  
  
  CONCLUSIONS
  Metformin is associated with higher tumor response rates to radiotherapy in rectal cancer, especially in patients with diabetes.
authors.affiliation: Department of Surgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, 81 Irwon-ro, Gangnam-gu, Seoul, 135-710, Korea.
authors.forename: Bo Young
authors.initials: BY
authors.lastname: Oh
authors.affiliation: Department of Surgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, 81 Irwon-ro, Gangnam-gu, Seoul, 135-710, Korea.
authors.forename: Yoon Ah
authors.initials: YA
authors.lastname: Park
authors.affiliation: Department of Surgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, 81 Irwon-ro, Gangnam-gu, Seoul, 135-710, Korea.
authors.forename: Jung Wook
authors.initials: JW
authors.lastname: Huh
authors.affiliation: Department of Surgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, 81 Irwon-ro, Gangnam-gu, Seoul, 135-710, Korea.
authors.forename: Yong Beom
authors.initials: YB
authors.lastname: Cho
authors.affiliation: Department of Surgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, 81 Irwon-ro, Gangnam-gu, Seoul, 135-710, Korea.
authors.forename: Seong Hyeon
authors.initials: SH
authors.lastname: Yun
authors.affiliation: Department of Surgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, 81 Irwon-ro, Gangnam-gu, Seoul, 135-710, Korea.
authors.forename: Woo Yong
authors.initials: WY
authors.lastname: Lee
authors.affiliation: Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Hee Chul
authors.initials: HC
authors.lastname: Park
authors.affiliation: Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Doo Ho
authors.initials: DH
authors.lastname: Choi
authors.affiliation: Division of Hematology-Oncology, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Young Suk
authors.initials: YS
authors.lastname: Park
authors.affiliation: Department of Surgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, 81 Irwon-ro, Gangnam-gu, Seoul, 135-710, Korea. hckim@skku.edu.
authors.forename: Hee Cheol
authors.initials: HC
authors.lastname: Kim
mesh_terms: D000368:Aged; D016022:Case-Control Studies; D059248:Chemoradiotherapy; D048909:Diabetes Complications; D005260:Female; D006801:Humans; D007004:Hypoglycemic Agents / Q000494:pharmacology*; D008297:Male; D008687:Metformin / Q000494:pharmacology*; D008875:Middle Aged; D012004:Rectal Neoplasms / Q000150:complications / Q000473:pathology / Q000532:radiotherapy*; D012008:Recurrence
chemical_list: D007004:Hypoglycemic Agents; D008687:Metformin
keywords: Diabetes; Metformin; Radiotherapy; Rectal cancer; Tumor response