title: Accuracy of positron emission tomography/computed tomography and clinical assessment in the detection of complete rectal tumor regression after neoadjuvant chemoradiation: long-term results of a prospective trial (National Clinical Trial 00254683).
abstract: BACKGROUND
  Neoadjuvant chemoradiation (CRT) therapy may result in significant tumor regression in patients with rectal cancer. Patients who develop complete tumor regression have been managed by treatment strategies that are alternatives to standard total mesorectal excision. Therefore, assessment of tumor response with positron emission tomography/computed tomography (PET/CT) after neoadjuvant treatment may offer relevant information for the selection of patients to receive alternative treatment strategies.
  
  
  METHODS
  Patients with clinical T2 (cT2) through cT4NxM0 rectal adenocarcinoma were included prospectively. Neoadjuvant therapy consisted of 54 grays of radiation and 5-fluorouracil-based chemotherapy. Baseline PET/CT studies were obtained before CRT followed by PET/CT studies at 6 weeks and 12 weeks after the completion of CRT. Clinical assessment was performed at 12 weeks after CRT completion. PET/CT results were compared with clinical and pathologic data.
  
  
  RESULTS
  In total, 99 patients were included in the study. Twenty-three patients were complete responders (16 had a complete clinical response, and 7 had a complete pathologic response). The PET/CT response evaluation at 12 weeks indicated that 18 patients had a complete response, and 81 patients had an incomplete response. There were 5 false-negative and 10 false-positive PET/CT results. PET/CT for the detection of residual cancer had 93% sensitivity, 53% specificity, a 73% negative predictive value, an 87% positive predictive value, and 85% accuracy. Clinical assessment alone resulted in an accuracy of 91%. PET/CT information may have detected misdiagnoses made by clinical assessment alone, improving overall accuracy to 96%.
  
  
  CONCLUSIONS
  Assessment of tumor response at 12 weeks after CRT completion with PET/CT imaging may provide a useful additional tool with good overall accuracy for the selection of patients who may avoid unnecessary radical resection after achieving a complete clinical response. Cancer 2012;3501-3511. © 2011 American Cancer Society.
authors.affiliation: Angelita and Joaquim Gama Institute, Sao Paulo, Brazil. rodrigo.operez@gmail.com
authors.forename: Rodrigo Oliva
authors.initials: RO
authors.lastname: Perez
authors.forename: Angelita
authors.initials: A
authors.lastname: Habr-Gama
authors.forename: Joaquim
authors.initials: J
authors.lastname: Gama-Rodrigues
authors.forename: Igor
authors.initials: I
authors.lastname: Proscurshim
authors.forename: Guilherme Pagin São
authors.initials: GP
authors.lastname: Julião
authors.forename: Patricio
authors.initials: P
authors.lastname: Lynn
authors.forename: Carla Rachel
authors.initials: CR
authors.lastname: Ono
authors.forename: Fabio Guilherme
authors.initials: FG
authors.lastname: Campos
authors.forename: Afonso Henrique
authors.initials: AH
authors.lastname: Silva e Sousa
authors.forename: Antonio Rocco
authors.initials: AR
authors.lastname: Imperiale
authors.forename: Sergio Carlos
authors.initials: SC
authors.lastname: Nahas
authors.forename: Carlos Alberto
authors.initials: CA
authors.lastname: Buchpiguel
mesh_terms: D000368:Aged; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use; D059248:Chemoradiotherapy / Q000379:methods; D017024:Chemotherapy, Adjuvant; D003131:Combined Modality Therapy; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging; D020360:Neoadjuvant Therapy / Q000379:methods; D049268:Positron-Emission Tomography; D012004:Rectal Neoplasms / Q000000981:diagnostic imaging* / Q000401:mortality / Q000628:therapy*; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome