title: Depth and lateral spread of microscopic residual rectal cancer after neoadjuvant chemoradiation: implications for treatment decisions.
abstract: OBJECTIVE
  The aim of this study was to determine the distribution of residual tumour within the bowel wall in relation to residual mucosal abnormalities (RMAs) and surrounding normal mucosa in patients with rectal cancer who underwent neoadjuvant chemoradiation followed by curative surgery.
  
  
  METHODS
  Archived pathological slides from a cohort of 60 patients with residual tumour were retrieved. The incidence, distance and depth of tumour spread (ypT) under RMAs and adjacent normal mucosa were reviewed and recorded.
  
  
  RESULTS
  Histological sections containing both RMA and adjacent normal mucosa were available for 45 of 60 patients with ypT1 (n = 6), ypT2 (n = 18) and ypT3 (n = 21) disease. The maximal depth of invasion, as measured by ypT stage, was found underneath the RMA in 44 of 45 (98%) patients. Microscopic tumour spread lateral to the RMA and under adjacent normal mucosa was found in 32 of 45 (71%) patients. The median and maximum distances of lateral spread for ypT1 tumours were 0 and 4 mm; for ypT2 were 2.5 and 9 mm; and for ypT3 were 4 and 9 mm respectively.
  
  
  CONCLUSIONS
  Lateral tumour spread under normal mucosa adjacent to RMAs is a common finding and extended up to 9 mm in this study. The epicentre for maximum depth of invasion was directly underneath the RMAs in nearly all cases. These data have clinical and technical implications if local excision is to be considered.
authors.affiliation: Department of Colorectal Surgery, Digestive Disease Institute, Cleveland Clinic, Cleveland, Ohio, USA.
authors.forename: F M
authors.initials: FM
authors.lastname: Smith
authors.forename: H
authors.initials: H
authors.lastname: Wiland
authors.forename: A
authors.initials: A
authors.lastname: Mace
authors.forename: R K
authors.initials: RK
authors.lastname: Pai
authors.forename: M F
authors.initials: MF
authors.lastname: Kalady
mesh_terms: D000230:Adenocarcinoma / Q000473:pathology* / Q000601:surgery / Q000628:therapy*; D059186:Chemoradiotherapy, Adjuvant; D003131:Combined Modality Therapy; D005260:Female; D006801:Humans; D008207:Lymphatic Metastasis; D008297:Male; D020360:Neoadjuvant Therapy; D009361:Neoplasm Invasiveness; D009367:Neoplasm Staging; D018365:Neoplasm, Residual; D012004:Rectal Neoplasms / Q000473:pathology* / Q000601:surgery / Q000628:therapy*
keywords: Rectal cancer; lateral spread; neoadjuvant; radiotherapy; restaging; tumour scatter