title: Predicting complete response to neoadjuvant CRT for distal rectal cancer using sequential PET/CT imaging.
abstract: BACKGROUND
  Molecular imaging using positron emission tomography/computerized tomography (PET/CT) may add relevant incremental diagnostic information to standard structural cross-sectional imaging. Such information may allow identification of patients with rectal cancer that are more likely to develop complete tumor regression after neoadjuvant chemoradiation therapy (CRT). The objective of this report was to identify PET/CT features that are associated with a complete response after CRT.
  
  
  METHODS
  99 cT2-4N0-2M0 distal rectal cancer patients (≤7 cm from anal verge) were included in this prospective single center trial (NCT 00254683). Patients underwent baseline PET/CT followed by 54 Gy and 5-fluorouracil-based neoadjuvant CRT. After completion of therapy, patients underwent 6- and 12-week PET/CT. Clinical assessment of tumor response was performed at 12 weeks and was blinded to radiological information. Patients were treated according to clinical assessment.
  
  
  RESULTS
  There were seven patients with a complete pathological response (pCR) and 16 with a complete clinical response (cCR) (23 complete responders). Comparison of pCR exclusively and non-pCR revealed that only baseline primary tumor standard uptake value (SUV) was a significant predictor of response. Comparison of complete responders (pCR or cCR) and non-complete responders showed that depth of rectal wall uptake at baseline PET/CT (p = 0.002) and variation between baseline and 12-week maximum standard uptake value (SUVmax) of primary tumor (p = 0.001) were independent predictors for complete response at multivariate analysis. A decrease >67 % between baseline and 6-week or 76 % between baseline and 12-week SUVmax were associated with complete response (pCR or cCR; p = 0.02 and p < 0.001, respectively).
  
  
  CONCLUSIONS
  Positron emission tomography/computerized tomography at baseline, 6 and 12 weeks, may provide information regarding patients with a higher likelihood of developing complete tumor regression following neoadjuvant CRT.
authors: Angelita and Joaquim Gama Institute, Rua Manuel da Nobrega, São Paulo, 1564, Brazil, rodrigo.operez@gmail.com.
authors: R O
authors: RO
authors: Perez
authors: A
authors: A
authors: Habr-Gama
authors: G P
authors: GP
authors: São Julião
authors: P B
authors: PB
authors: Lynn
authors: C
authors: C
authors: Sabbagh
authors: I
authors: I
authors: Proscurshim
authors: F G
authors: FG
authors: Campos
authors: J
authors: J
authors: Gama-Rodrigues
authors: S C
authors: SC
authors: Nahas
authors: C A
authors: CA
authors: Buchpiguel
mesh_terms: D000230:Adenocarcinoma / Q000175:diagnosis / Q000628:therapy*; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D059186:Chemoradiotherapy, Adjuvant; D003952:Diagnostic Imaging; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D020360:Neoadjuvant Therapy; D009367:Neoplasm Staging; D049268:Positron-Emission Tomography / Q000379:methods*; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012004:Rectal Neoplasms / Q000175:diagnosis / Q000628:therapy*; D015203:Reproducibility of Results; D013997:Time Factors; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome
chemical_list: D000970:Antineoplastic Agents