title: ¹⁸F-FDG PET/CT and Colorectal Cancer: Value of Fourth and Subsequent Posttherapy Follow-up Scans for Patient Management.
abstract: The purpose of this study was to evaluate the added value of a fourth and subsequent follow-up PET/CT scans to clinical assessment and impact on patient management in patients with colorectal cancer.
  
  
  METHODS
  This was an institutional review board-approved, retrospective study. Eight hundred twenty-two patients with biopsy-proven colorectal cancer, who underwent (18)F-FDG PET/CT, were identified from 2000 to 2012. Among these, 73 (8.9%) patients underwent 4 or more follow-up PET/CT scans, with a total of 313 fourth and subsequent follow-up PET/CT scans. Median follow-up from the fourth follow-up PET/CT scan was 41.7 mo. The added value of each follow-up PET/CT scan, for clinical assessment and the treatment changes subsequent to each follow-up PET/CT scan, was established. Overall survival prediction was established using Kaplan-Meier plots with a Mantel-Cox log-rank test.
  
  
  RESULTS
  Of the 313 fourth and subsequent follow-up PET/CT scans, 174 (55.6%) were interpreted as positive and 139 (44.4%) were interpreted as negative for recurrence or metastases. Thirty-four (46.6%) patients died during the study period. PET/CT identified recurrence or metastasis in 40.0% of scans obtained without prior clinical suspicion and ruled out disease in 23.6% of scans obtained with prior clinical suspicion. The PET/CT scan resulted in treatment change after 34.2% (107/313) of the scans. New treatment was initiated after 24.0% (75/313) of the scans, and treatment was changed after 8.0% (25/313) scans. There was a statistically significant difference in the overall survival between patients with a positive and all negative fourth and subsequent follow-up PET/CT scans at the patient level (log-rank, P = 0.001).
  
  
  CONCLUSIONS
  The fourth and subsequent (18)F-FDG PET/CT scans obtained after primary treatment completion add value to clinical assessment and the management plan and provide prognostic information in patients with colorectal cancer.
authors.affiliation: Russell H. Morgan Department of Radiology and Radiological Sciences, Johns Hopkins University, Baltimore, Maryland.
authors.forename: Charles
authors.initials: C
authors.lastname: Marcus
authors.affiliation: Russell H. Morgan Department of Radiology and Radiological Sciences, Johns Hopkins University, Baltimore, Maryland.
authors.forename: Wael
authors.initials: W
authors.lastname: Marashdeh
authors.affiliation: Russell H. Morgan Department of Radiology and Radiological Sciences, Johns Hopkins University, Baltimore, Maryland.
authors.forename: Se Jin
authors.initials: SJ
authors.lastname: Ahn
authors.affiliation: Russell H. Morgan Department of Radiology and Radiological Sciences, Johns Hopkins University, Baltimore, Maryland.
authors.forename: Mehdi
authors.initials: M
authors.lastname: Taghipour
authors.affiliation: Russell H. Morgan Department of Radiology and Radiological Sciences, Johns Hopkins University, Baltimore, Maryland Department of Oncology of Johns Hopkins School of Medicine, Johns Hopkins University, Baltimore, Maryland; and Department of Health Policy and Management, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland rsubram4@jhmi.edu.
authors.forename: Rathan M
authors.initials: RM
authors.lastname: Subramaniam
mesh_terms: D000368:Aged; D001706:Biopsy; D015179:Colorectal Neoplasms / Q000000981:diagnostic imaging*; D057286:Electronic Health Records; D005260:Female; D019788:Fluorodeoxyglucose F18; D005500:Follow-Up Studies; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D009362:Neoplasm Metastasis; D049268:Positron-Emission Tomography; D011379:Prognosis; D016016:Proportional Hazards Models; D012008:Recurrence; D012042:Registries; D012189:Retrospective Studies; D013997:Time Factors; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome
chemical_list: D019788:Fluorodeoxyglucose F18
keywords: PET/CT; clinical suspicion; colorectal cancer; follow-up; recurrence; treatment change