title: Detection of skeletal muscle metastasis: torso FDG PET-CT versus contrast-enhanced chest or abdomen CT.
abstract: BACKGROUND
  Skeletal muscle metastasis (SMM) in cancer patients has not been sufficiently evaluated regarding prevalence and proper method of detection.
  
  
  OBJECTIVE
  To determine the prevalence of SMM and compare the diagnostic competencies for SMM of torso F-18 fluorodeoxyglucose (FDG) positron emission tomography-computed tomography (PET-CT) and contrast-enhanced chest or abdomen CT.
  
  
  METHODS
  We investigated 18,225 PET-CT studies of 6359 cancer patients performed from 2005 to 2012. The PET-CT studies describing potential SMM were retrieved and the corresponding medical records were reviewed. The gold standard for SMM was histopathologically-proven SMM or imaging study-based disease progression. The detectability of SMM was compared between PET-CT and contrast-enhanced CT.
  
  
  RESULTS
  Twenty-six patients had 84 SMM lesions, representing a SMM prevalence of 0.41%. Lung cancer was the most common SMM-associated malignancy (54%) and the gluteal/pelvic girdle muscle was the most frequently involved SMM site (37%). All 84 SMM lesions were visualized on PET-CT (100%). Of these PET-CT positive 84 SMM lesions, 51 lesions were in the CT field of view (FOV) (61%), whereas 33 lesions were out of the CT FOV (39%). Among these 51 lesions, 17 lesions showed rim-enhancing nodules/masses (33%), eight lesions showed homogeneously enhancing nodules (16%), three lesions showed heterogeneously enhancing nodules (6%), and 23 SMM lesions (45%) were non-diagnostic by CT. All 51 SMM lesions within CT FOV were detected on PET-CT (100%), whereas only 28 were visualized on CT (54.9%), resulting in a significant difference (P < 0.005). On average, 2.6 more organs with concomitant metastases were found when SMM was revealed by PET-CT.
  
  
  CONCLUSIONS
  The prevalence of SMM was as low as 0.41% in the current large cohort of cancer patients. Torso PET-CT was a more competent modality than contrast-enhanced CT in the detection of SMM.
authors.affiliation: Department of Nuclear Medicine, Konkuk University Medical Center, Konkuk University School of Medicine, Seoul, Republic of Korea.
authors.forename: Young
authors.initials: Y
authors.lastname: So
authors.affiliation: Department of Radiology, Konkuk University Medical Center, Konkuk University School of Medicine, Seoul, Republic of Korea Research Institute of Medical Science, Konkuk University School of Medicine, Seoul, Republic of Korea jgyi92@gmail.com.
authors.forename: Jeong Geun
authors.initials: JG
authors.lastname: Yi
authors.affiliation: Department of Radiology, Konkuk University Medical Center, Konkuk University School of Medicine, Seoul, Republic of Korea.
authors.forename: Inyoung
authors.initials: I
authors.lastname: Song
authors.affiliation: Department of Nuclear Medicine, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam, Republic of Korea.
authors.forename: Won Woo
authors.initials: WW
authors.lastname: Lee
authors.affiliation: Department of Nuclear Medicine, Konkuk University Medical Center, Konkuk University School of Medicine, Seoul, Republic of Korea.
authors.forename: Hyun Woo
authors.initials: HW
authors.lastname: Chung
authors.affiliation: Department of Radiology, Konkuk University Medical Center, Konkuk University School of Medicine, Seoul, Republic of Korea.
authors.forename: Jeong Hee
authors.initials: JH
authors.lastname: Park
authors.affiliation: Department of Radiology, Konkuk University Medical Center, Konkuk University School of Medicine, Seoul, Republic of Korea.
authors.forename: Sung Gyu
authors.initials: SG
authors.lastname: Moon
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003287:Contrast Media; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007723:Korea / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging / Q000379:methods; D019042:Muscle Neoplasms / Q000175:diagnosis* / Q000556:secondary*; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging; D049268:Positron-Emission Tomography; D015995:Prevalence; D011856:Radiographic Image Enhancement / Q000379:methods; D011860:Radiography, Abdominal; D013902:Radiography, Thoracic; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed; D060726:Torso / Q000000981:diagnostic imaging
chemical_list: D003287:Contrast Media; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18
keywords: Computed tomography (CT); malignancy; metastasis; neoplasm; positron emission tomography-computed tomography (PET-CT); skeletal muscle