title: Diabetes mellitus affects response to neoadjuvant chemoradiotherapy in the management of rectal cancer.
abstract: BACKGROUND
  Although diabetic patients with rectal cancer have poorer outcomes than their nondiabetic counterparts, few studies have looked at diabetics' response to therapy as an explanation for this disparity. This study compares the neoadjuvant chemoradiotherapy (CRT) response in diabetic and nondiabetic patients with locally advanced rectal cancers.
  
  
  METHODS
  This is a single-institution, retrospective review of rectal cancer patients who received CRT followed by resection from 1995 to 2006. Pretreatment tumor-node-metastasis (TNM) staging was determined using endorectal ultrasound, computed tomography (CT) scan, and magnetic resonance imaging (MRI); post-treatment staging was determined by pathological review.
  
  
  RESULTS
  110 patients were included; seventeen had diabetes and 93 were nondiabetics. Pretreatment staging was similar in both groups. Sixteen of the diabetics (94%) completed CRT compared to 92% (86/93) of the nondiabetics. Tumor downstaging rates were similar in the two groups (53% in diabetics, 52% in nondiabetics). Nondiabetic patients had a higher rate of nodal downstaging although not statistically significant (67% versus 27%, P = 0.80). While none of the diabetics patients achieved a pathologic complete response (pCR), 23% (21/93) of the nondiabetics did (P = 0.039). Local progression rates were higher in the diabetic group (24% versus 5%, P = 0.046).
  
  
  CONCLUSIONS
  Our study shows that neoadjuvant chemoradiotherapy in rectal cancer is less effective in diabetic patients than in nondiabetics. While minimal differences are found in the rate of downstaging, the rate of achieving a complete pathologic response was significantly higher in nondiabetic patients, and in fact was not seen in any of our diabetic patients. This may explain the poorer outcomes seen in diabetic patients with rectal cancer.
authors.affiliation: Division of Surgical Oncology, University of North Carolina, Chapel Hill, NC, USA.
authors.forename: A S
authors.initials: AS
authors.lastname: Caudle
authors.forename: H J
authors.initials: HJ
authors.lastname: Kim
authors.forename: J E
authors.initials: JE
authors.lastname: Tepper
authors.forename: B H
authors.initials: BH
authors.lastname: O'Neil
authors.forename: L A
authors.initials: LA
authors.lastname: Lange
authors.forename: R M
authors.initials: RM
authors.lastname: Goldberg
authors.forename: S A
authors.initials: SA
authors.lastname: Bernard
authors.forename: B F
authors.initials: BF
authors.lastname: Calvo
authors.forename: M O
authors.initials: MO
authors.lastname: Meyers
mesh_terms: D000328:Adult; D000368:Aged; D000970:Antineoplastic Agents / Q000627:therapeutic use; D048909:Diabetes Complications; D003920:Diabetes Mellitus; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D020360:Neoadjuvant Therapy; D009367:Neoplasm Staging; D011878:Radiotherapy; D012004:Rectal Neoplasms / Q000150:complications / Q000473:pathology* / Q000628:therapy*; D012189:Retrospective Studies; D016896:Treatment Outcome
chemical_list: D000970:Antineoplastic Agents