title: PET-CT fusion in radiation management of patients with anorectal tumors.
abstract: OBJECTIVE
  To compare computed tomography (CT) with positron emission tomography-CT (PET-CT) scans with respect to anorectal tumor volumes, correlation in overlap, and influence on radiation treatment fields and patient care.
  
  
  METHODS
  From March to November 2003, 20 patients with rectal cancer and 3 patients with anal cancer were treated with preoperative or definitive chemoradiation, respectively. Computed tomography simulation data generated a CT gross tumor volume (CT-GTV) and CT planning target volume (CT-PTV) and (18)F-fluoro-2-deoxy-glucose PET (FDG-PET) created a PET-GTV and PET-PTV. The PET-CT and CT images were fused using manual coregistration. Patients were treated with three-dimensional conformal therapy to traditional doses. The PET, CT, and overlap volumes (OVs) were measured in cubic centimeters.
  
  
  RESULTS
  Mean PET-GTV was smaller than the mean CT-GTV (91.7 vs. 99.6 cm(3)). The mean OV was 46.7%. As tumor volume increased, PET and CT OV correlated significantly (p < 0.001). In 17% of patients PET-CT altered the PTV, and in 26% it changed the radiation treatment plan. For 25% of patients with rectal cancer, PET detected distant metastases and changed overall management. Ten rectal cancer patients underwent surgery. When the pretreatment PET standardized uptake value was >10 and the posttreatment PET standardized uptake value was <6, 100% achieved pathologic downstaging (p = 0.047).
  
  
  CONCLUSIONS
  Variation in volume was significant, with 17% and 26% of patients requiring a change in treatment fields and patient management, respectively. Positron emission tomography can change the management for anorectal tumors by early detection of metastatic disease or disease outside standard radiation fields.
authors: Department of Radiation Oncology, Emory University School of Medicine, Atlanta, GA 30322, USA.
authors: Cynthia
authors: C
authors: Anderson
authors: Mary
authors: M
authors: Koshy
authors: Charles
authors: C
authors: Staley
authors: Natia
authors: N
authors: Esiashvili
authors: Sharam
authors: S
authors: Ghavidel
authors: Zach
authors: Z
authors: Fowler
authors: Tim
authors: T
authors: Fox
authors: Fabio
authors: F
authors: Esteves
authors: Jerome
authors: J
authors: Landry
authors: Karen
authors: K
authors: Godette
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001005:Anus Neoplasms / Q000000981:diagnostic imaging* / Q000188:drug therapy / Q000532:radiotherapy; D003131:Combined Modality Therapy / Q000379:methods; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals; D020266:Radiotherapy, Conformal / Q000379:methods; D012004:Rectal Neoplasms / Q000000981:diagnostic imaging* / Q000188:drug therapy / Q000532:radiotherapy; D014057:Tomography, X-Ray Computed / Q000379:methods*; D047368:Tumor Burden
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18