title: MRI demonstration of the effect of neoadjuvant radiotherapy on rectal carcinoma.
abstract: OBJECTIVE
  In patients with locally advanced rectal cancer, neoadjuvant long course (45-54 Gy in 25-30 fractions) chemoradiotherapy (CRT) may reduce tumour size and result in downstaging. In patients with primary resectable tumour short course (25 Gy in 5 fractions) radiotherapy (SCRT) reduces local recurrence but downstaging the disease or altering tumour size has not been described. We aimed to assess change in tumour size on MRI after SCRT or CRT.
  
  
  METHODS
  Nineteen patients with rectal carcinoma underwent MRI before and after SCRT or CRT. In each case, tumour length and width were documented and number of locoregional lymph nodes recorded. Total mesorectal excision was performed in 15 patients and MR findings correlated with histopathology.
  
  
  RESULTS
  Ten patients received SCRT and nine CRT. Tumour length reduced by 19% overall (15% following SCRT, 23% following CRT). Greater than 30% reduction (partial response) in maximum tumour thickness was seen in 4/10 (40%) following SCRT and 5/9 (56%) following CRT.
  
  
  CONCLUSIONS
  Significant reduction in tumour size can be achieved with preoperative long course CRT and SCRT. This unexpected finding following SCRT has not been previously described.
authors.affiliation: Academic Department of Radiology, St. Bartholomews' Hospital, London, UK. audreyejacques@yahoo.co.uk
authors.forename: Audrey E T
authors.initials: AE
authors.lastname: Jacques
authors.forename: Andrea G
authors.initials: AG
authors.lastname: Rockall
authors.forename: Mandana
authors.initials: M
authors.lastname: Alijani
authors.forename: John
authors.initials: J
authors.lastname: Hughes
authors.forename: Syed
authors.initials: S
authors.lastname: Babar
authors.forename: Jo-Anne Chin
authors.initials: JA
authors.lastname: Aleong
authors.forename: Chris
authors.initials: C
authors.lastname: Cottrill
authors.forename: Sina
authors.initials: S
authors.lastname: Dorudi
authors.forename: Rodney H
authors.initials: RH
authors.lastname: Reznek
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002277:Carcinoma / Q000175:diagnosis* / Q000473:pathology / Q000532:radiotherapy*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D020360:Neoadjuvant Therapy; D012004:Rectal Neoplasms / Q000175:diagnosis* / Q000473:pathology / Q000532:radiotherapy*; D016896:Treatment Outcome