title: PET scans as a predictive marker of survival in advanced colorectal cancer.
abstract: BACKGROUND
  The clinical utility of fluorodeoxyglucose (FDG)-positron emission tomography (PET) scan in predicting the outcome of patients with metastatic colorectal cancer (mCRC) has not been well studied. We hypothesized that standardized uptake value (SUV) in FDG-PET scans after treatment predicts outcomes among patients with mCRC.
  
  
  METHODS
  We retrospectively reviewed mCRC patients who had FDG-PET scans before their treatment and measured their SUV on follow-up imaging at the Karmanos Cancer Institute. Primary end points of time to progression (TTP) and overall survival (OS) were compared in 2 groups: follow-up (posttreatment) SUV of 0 versus > 0.
  
  
  RESULTS
  The study population consisted of 44 patients (median age of 58.1 years). Forty (91%) of the patients were treated first-line, 34 (77%) received an oxaliplatin-based regimen, and 7 (16%) received an irinotecan-based regimen. Thirty-four (77%) patients received concurrent bevacizumab. Median pretreatment SUV was 9.2 (range, 1.7-46.3), and median posttreatment SUV (in n = 41) was 4.0 (range, 0-14). The median percent change in SUV was -68.5% (range, -9.2% to -100%). The median time interval between scans was 2.6 months. There was no statistically significant difference noted between metabolic responders and nonresponders with regard to TTP and OS. However, patients with a posttreatment SUV of 0 had significantly longer OS than those with posttreatment SUV of > 0 (median, 42 vs. 25.2 months, respectively), and slightly longer TTP (median, 8.2 vs. 6.9 months, respectively).
  
  
  CONCLUSIONS
  Systemic therapy significantly decreased SUV on follow-up PET scans in advanced colorectal cancer patients. Absence of FDG uptake on follow-up PET scans was associated with markedly longer OS and slightly longer TTP.
authors.affiliation: Department of Medicine, Stony Brook University, Stony Brook, NY. Electronic address: Minsig.choi@stonybrookmedicine.edu.
authors.forename: Minsig
authors.initials: M
authors.lastname: Choi
authors.affiliation: Division of Hematology and Oncology, Providence Hospital, Southfield, MI.
authors.forename: Sri Lakshmi S
authors.initials: SL
authors.lastname: Kollepara
authors.affiliation: Karmanos Cancer Institute, Wayne State University School of Medicine, Detroit, MI.
authors.forename: Lance K
authors.initials: LK
authors.lastname: Heilbrun
authors.affiliation: Karmanos Cancer Institute, Wayne State University School of Medicine, Detroit, MI.
authors.forename: Daryn
authors.initials: D
authors.lastname: Smith
authors.affiliation: Karmanos Cancer Institute, Wayne State University School of Medicine, Detroit, MI.
authors.forename: Anthony F
authors.initials: AF
authors.lastname: Shields
authors.affiliation: Karmanos Cancer Institute, Wayne State University School of Medicine, Detroit, MI.
authors.forename: Philip A
authors.initials: PA
authors.lastname: Philip
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use*; D015179:Colorectal Neoplasms / Q000188:drug therapy / Q000473:pathology*; D018572:Disease-Free Survival; D005260:Female; D019788:Fluorodeoxyglucose F18; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D009362:Neoplasm Metastasis; D049268:Positron-Emission Tomography / Q000379:methods*; D012189:Retrospective Studies; D015996:Survival Rate; D016896:Treatment Outcome
chemical_list: D019788:Fluorodeoxyglucose F18
keywords: Metabolic response; Metastatic colorectal cancer; Prognostic marker; Systemic chemotherapy; Treatment response