title: Clinical implications of quantification of mesorectal tumor invasion by endoscopic ultrasound: All T3 rectal cancers are not equal.
abstract: BACKGROUND
  Depth of invasion beyond the muscularis propria (MP) by T3 rectal cancer can vary. The purpose of the present paper was to determine if depth of invasion beyond MP, as assessed by preoperative endoscopic ultrasound (EUS), can predict tumor recurrence in patients with T3 rectal tumors.
  
  
  METHODS
  Patients with T3NxM0 rectal cancer, as determined by EUS, who underwent surgical resection (without preoperative neoadjuvant therapy) were reviewed by two blinded endosonographers. Tumors were classified as minimally invasive T3 (invasion </= 2 mm beyond MP by EUS) and advanced T3 disease (invasion > 2 mm).
  
  
  RESULTS
  Forty-two patients with T3 rectal tumors underwent surgical resection without receiving preoperative neoadjuvant therapy, of whom 14 had minimally invasive T3 and 28 had advanced T3 disease, as determined by preoperative EUS. Median follow up was 19 months. Tumor recurrence rates in minimally invasive and advanced T3 tumors were 14.3% and 39.3%, respectively, P = 0.02 (log-rank test). Adjusting for nodal status and postoperative adjuvant therapy administration, Cox proportional hazards model demonstrated advanced T3 disease (by EUS) to predict tumor recurrence, hazard ratio, 2.28 (95% confidence interval: 1.17-5.81), P = 0.01.
  
  
  CONCLUSIONS
  All T3 rectal tumors are not equal, with minimally invasive disease carrying a more favorable prognosis. By discriminating minimally invasive from advanced T3 disease, preoperative EUS provides important prognostic information. Further subclassification of T3 tumors, based on preoperative EUS staging, should be considered to enhance selection of patients for neoadjuvant therapy.
authors.affiliation: Department of Gastroenterology and Hepatology, Mayo Clinic, Minnesota, USA. harewood.gavin@mayo.edu
authors.forename: Gavin C
authors.initials: GC
authors.lastname: Harewood
authors.forename: K Shiva
authors.initials: KS
authors.lastname: Kumar
authors.forename: Jonathan E
authors.initials: JE
authors.lastname: Clain
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Levy
authors.forename: Heidi
authors.initials: H
authors.lastname: Nelson
mesh_terms: D000368:Aged; D018572:Disease-Free Survival; D019160:Endosonography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009361:Neoplasm Invasiveness; D009364:Neoplasm Recurrence, Local; D009367:Neoplasm Staging / Q000379:methods*; D012004:Rectal Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery; D016896:Treatment Outcome