title: A comparative study of volumetric analysis, histopathologic downstaging, and tumor regression grade in evaluating tumor response in locally advanced rectal cancer following preoperative chemoradiation.
abstract: OBJECTIVE
  To compare tumor volume reduction rate, histopathologic downstaging, and tumor regression grade (TRG) among tumor responses in rectal cancer after preoperative chemoradiotherapy (CRT).
  
  
  METHODS
  Between 2002 and 2004, 30 patients with locally advanced rectal cancer underwent preoperative CRT, followed by surgical resection. Magnetic resonance volumetry was performed before and after CRT. Histopathologic tumor staging and tumor regression were reviewed. We compared pre- and post-CRT tumor volume and percent of volume reduction, according to histopathologic downstaging and TRG.
  
  
  RESULTS
  The tumor volume reduction rates ranged from 14.6% to 100%. Mean pre- and post-CRT tumor volumes were significantly smaller in patients who showed T downstaging than in those who did not (p = 0.040, 0.014). The mean tumor volume reduction was 66.4% vs. 55.2% (p = 0.361). However, the mean pre- and post-CRT tumor volume and mean tumor volume reduction rate between patients who showed N downstaging and those who did not were not statistically different (p = 0.176, 0.767, and 0.899). With respect to TRG, the mean pre- and post-CRT tumor volumes were not statistically significant (p = 0.108, 0.708, and 0.120).
  
  
  CONCLUSIONS
  Tumor volume reduction rate does not correlate with histopathologic downstaging and TRG. It might be hazardous to evaluate tumor response with respect to volume reduction and to select the surgical method on this basis.
authors.affiliation: Colorectal Cancer Clinic Severance Hospital, Yonsei University Medical Center, Seoul, Republic of Korea. namkyuk@yumc.yonsei.ac.kr
authors.forename: Nam Kyu
authors.initials: NK
authors.lastname: Kim
authors.forename: Seung Hyuk
authors.initials: SH
authors.lastname: Baik
authors.forename: Byung Soh
authors.initials: BS
authors.lastname: Min
authors.forename: Hong Ryull
authors.initials: HR
authors.lastname: Pyo
authors.forename: Yun Jung
authors.initials: YJ
authors.lastname: Choi
authors.forename: Hogeun
authors.initials: H
authors.lastname: Kim
authors.forename: Jinsil
authors.initials: J
authors.lastname: Seong
authors.forename: Ki Chang
authors.initials: KC
authors.lastname: Keum
authors.forename: Sun Young
authors.initials: SY
authors.lastname: Rha
authors.forename: Hyun Cheol
authors.initials: HC
authors.lastname: Chung
mesh_terms: D000328:Adult; D000368:Aged; D003131:Combined Modality Therapy / Q000379:methods; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging / Q000379:methods; D011446:Prospective Studies; D012004:Rectal Neoplasms / Q000188:drug therapy / Q000473:pathology / Q000532:radiotherapy / Q000601:surgery; D012074:Remission Induction; D018709:Statistics, Nonparametric; D014463:Ultrasonography