title: Role of biopsies in patients with residual rectal cancer following neoadjuvant chemoradiation after downsizing: can they rule out persisting cancer?
abstract: OBJECTIVE
  The study aimed to determine the value of postchemoradiation biopsies, performed after significant tumour downsizing following neoadjuvant therapy, in predicting complete tumour regression in patients with distal rectal cancer.
  
  
  METHODS
  A retrospective comparative study was performed in patients with rectal cancer who achieved an incomplete clinical response after neoadjuvant chemoradiotherapy. Patients with significant tumour downsizing (> 30% of the initial tumour size) were compared with controls (< 30% reduction of the initial tumour size). During flexible proctoscopy carried out postchemoradiation, biopsies were performed using 3-mm biopsy forceps. The biopsy results were compared with the histopathological findings of the resected specimen. UICC (Union for International Cancer Control) ypTNM classification, tumour differentiation and regression grade were evaluated. The main outcome measures were sensitivity and specificity, negative and positive predictive values, and accuracy of a simple forceps biopsy for predicting pathological response after neoadjuvant chemoradiotherapy.
  
  
  RESULTS
  Of the 172 patients, 112 were considered to have had an incomplete clinical response and were included in the study. Thirty-nine patients achieved significant tumour downsizing and underwent postchemoradiation biopsies. Overall, 53 biopsies were carried out. Of the 39 patients who achieved significant tumour downsizing, the biopsy result was positive in 25 and negative in 14. Only three of the patients with a negative biopsy result were found to have had a complete pathological response (giving a negative predictive value of 21%). Considering all biopsies performed, only three of 28 negative biopsies were true negatives, giving a negative predictive value of 11%.
  
  
  CONCLUSIONS
  In patients with distal rectal cancer undergoing neoadjuvant chemoradiation, post-treatment biopsies are of limited clinical value in ruling out persisting cancer. A negative biopsy result after a near-complete clinical response should not be considered sufficient for avoiding a radical resection.
authors.affiliation: Colorectal Surgery Division, University of São Paulo, School of Medicine Angelita & Joaquim Gama Institute, São Paulo, Brazil. rodrigo.operez@gmail.com
authors.forename: R O
authors.initials: RO
authors.lastname: Perez
authors.forename: A
authors.initials: A
authors.lastname: Habr-Gama
authors.forename: G V
authors.initials: GV
authors.lastname: Pereira
authors.forename: P B
authors.initials: PB
authors.lastname: Lynn
authors.forename: P A
authors.initials: PA
authors.lastname: Alves
authors.forename: I
authors.initials: I
authors.lastname: Proscurshim
authors.forename: V
authors.initials: V
authors.lastname: Rawet
authors.forename: J
authors.initials: J
authors.lastname: Gama-Rodrigues
mesh_terms: D000230:Adenocarcinoma / Q000473:pathology* / Q000628:therapy*; D000328:Adult; D000368:Aged; D001706:Biopsy; D059186:Chemoradiotherapy, Adjuvant; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D020360:Neoadjuvant Therapy; D009367:Neoplasm Staging; D018365:Neoplasm, Residual; D011237:Predictive Value of Tests; D011351:Proctoscopy; D012004:Rectal Neoplasms / Q000473:pathology* / Q000628:therapy*; D012189:Retrospective Studies; D047368:Tumor Burden