title: Posttreatment FDG-PET-CT response is predictive of tumor progression and survival in anal carcinoma.
abstract: OBJECTIVE
  We hypothesize that posttreatment F-18 fluorodeoxyglucose positron emission tomography-computed tomography (FDG PET-CT) metabolic response predicts clinical outcomes in patients with anal cancer treated with chemoradiation.
  
  
  METHODS
  This was a single-institution retrospective review of 148 patients treated definitively for anal squamous cell carcinoma between 2005 and 2012. All patients were followed with posttreatment PET-CT scans and clinical examinations. Progression-free survival (PFS), cause-specific survival, and overall survival (OS) estimates were calculated using the Kaplan-Meier method.
  
  
  RESULTS
  The median follow-up was 34 months (range, 5-89 months). Pretreatment PET was successful in detecting the primary tumor in 140 cases (95%). Computed tomography (CT) alone was able to detect primary tumors in 78 of 122 patients who had pretreatment CT scans (64%). Inguinal or pelvic lymph nodes were FDG avid in 68 patients, with only 41 of these patients having enlarged lymph nodes by CT criteria (60.3%). Initial posttreatment PET-CT was obtained on average 12.7 ± 4.3 weeks after the last day of radiation (range, 5-25 weeks). Overall complete metabolic response (CR) on initial PET-CT was found in 82 patients (58%). Partial metabolic response was noted in 52 (36.9%) and progression in 7 patients (5%). Only 12/82 patients (14.6%) with a FDG-PET CR eventually recurred. The negative predictive value of a PET-CT scan performed between 13 and 25 weeks posttreatment was 92.9%. The 2-year PFS for patients with CR versus non-CR was 89.8% and 69.2%, respectively (P = .004). The 2-year OS for CR versus non-CR patients was 94.8% and 79.3% (P = .036).
  
  
  CONCLUSIONS
  Complete metabolic response on posttreatment FDG PET-CT is highly predictive of increased PFS and OS in patients treated with chemoradiation for anal carcinoma. In addition to close clinical surveillance, we recommend obtaining posttreatment PET-CT scans >12 weeks following definitive treatment for anal cancer.
authors.affiliation: Department of Radiation Oncology, Kaiser Permanente Los Angeles Medical Center, Los Angeles, California; Department of Radiation Oncology, Southern California Permanente Medical Group, Los Angeles, California.
authors.forename: Kelly E
authors.initials: KE
authors.lastname: Goldman
authors.affiliation: Department of Radiation Oncology, Kaiser Permanente Los Angeles Medical Center, Los Angeles, California; Department of Radiation Oncology, Southern California Permanente Medical Group, Los Angeles, California. Electronic address: ewhite1@gmail.com.
authors.forename: Evan C
authors.initials: EC
authors.lastname: White
authors.affiliation: Department of Radiation Oncology, Southern California Permanente Medical Group, Los Angeles, California.
authors.forename: Aroor R
authors.initials: AR
authors.lastname: Rao
authors.affiliation: Research Laboratory, Southern California Permanente Medical Group, Los Angeles, California.
authors.forename: John S
authors.initials: JS
authors.lastname: Kaptein
authors.affiliation: Department of Radiation Oncology, Southern California Permanente Medical Group, Los Angeles, California.
authors.forename: Winston W
authors.initials: WW
authors.lastname: Lien
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001005:Anus Neoplasms / Q000000981:diagnostic imaging*; D018450:Disease Progression; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000378:metabolism*; D006801:Humans; D008297:Male; D008875:Middle Aged; D000072078:Positron Emission Tomography Computed Tomography / Q000379:methods*; D012189:Retrospective Studies
chemical_list: D019788:Fluorodeoxyglucose F18