title: Contrast-enhanced [18F] fluorodeoxyglucose-positron emission tomography-computed tomography as an initial imaging modality in patients presenting with metastatic malignancy of undefined primary origin.
abstract: BACKGROUND
  To evaluate the advantages of contrast enhanced F-18-fluorodeoxyglucose (FDG) positron emission tomography-computed tomography (PET-contrast enhanced CT [CECT]) when used as an initial imaging modality in patients presenting with metastatic malignancy of undefined primary origin (MUO).
  
  
  METHODS
  A total of 243 patients with fine needle aspiration cytology/biopsy proven MUO were included in this prospective study. Patients who were thoroughly evaluated for primary or primary tumor was detected by any other investigation were excluded from the analysis. Totally, 163 patients with pathological diagnosis of malignancy but no apparent sites of the primary tumor were finally selected for analysis. The site of probable primary malignancy suggested by PET-CECT was confirmed by biopsy/follow-up.
  
  
  RESULTS
  PET-CECT suggested probable site of primary in 128/163 (78.52%) patients. In 30/35 remaining patients, primary tumor was not detected even after extensive work-up. In 5 patients, where PET-CECT was negative, primary was found on further extensive investigations or follow-up. The sensitivity, specificity, positive predictive value and negative predictive value of the study were 95.76%, 66.67%, 88.28% and 85.71% respectively.
  
  
  CONCLUSIONS
  F-18 FDG PET-CECT aptly serves the purpose of initial imaging modality owing to high sensitivity, negative and positive predictive value. PET-CECT not only surveys the whole body for the primary malignancy but also stages the disease accurately. Use of contrast improves the diagnostic utility of modality as well as help in staging of the primary tumor. Although benefits of using PET-CECT as initial diagnostic modality are obvious from this study, there is a need for a larger study comparing conventional methods for diagnosing primary in patients with MUO versus PET-CECT.
authors.affiliation: Department of Nuclear Medicine and PET-CT, Apollo Hospitals, Chennai, Tamil Nadu, India.
authors.forename: Avani
authors.initials: A
authors.lastname: Jain
authors.affiliation: Department of Nuclear Medicine, JIPMER, Puducherry, India.
authors.forename: Madhur Kumar
authors.initials: MK
authors.lastname: Srivastava
authors.affiliation: Department of Nuclear Medicine and PET-CT, HCG Manavata Cancer Centre, Nashik, Maharashtra, India.
authors.forename: Alok Suresh
authors.initials: AS
authors.lastname: Pawaskar
authors.affiliation: Department of Nuclear Medicine and PET-CT, Apollo Hospitals, Chennai, Tamil Nadu, India.
authors.forename: Simon
authors.initials: S
authors.lastname: Shelley
authors.affiliation: Department of Nuclear Medicine and PET-CT, Apollo Hospitals, Chennai, Tamil Nadu, India.
authors.forename: Indirani
authors.initials: I
authors.lastname: Elangovan
authors.affiliation: Department of Nuclear Medicine, Kailash Cancer Hospital and Research Institute, Vadodara, Gujarat, India.
authors.forename: Hasmukh
authors.initials: H
authors.lastname: Jain
authors.affiliation: Department of Nuclear Medicine, Eko Diagnostic Center, Kolkata, West Bengal, India.
authors.forename: Somnath
authors.initials: S
authors.lastname: Pandey
authors.affiliation: Department of Nuclear Medicine and PET-CT, Apollo Hospitals, Chennai, Tamil Nadu, India.
authors.forename: Shilpa
authors.initials: S
authors.lastname: Kalal
authors.affiliation: Department of Nuclear Medicine and PET-CT, Apollo Hospitals, Chennai, Tamil Nadu, India.
authors.forename: Jaykanth
authors.initials: J
authors.lastname: Amalachandran
keywords: Contrast enhanced computed tomography; fluorodeoxyglucose positron emission tomography-computed tomography; malignancy of undefined primary origin; probable primary; unknown primary