title: Viable tumor volume: Volume of interest within segmented metastatic lesions, a pilot study of proposed computed tomography response criteria for urothelial cancer.
abstract: OBJECTIVE
  To evaluate the ability of new computed tomography (CT) response criteria for solid tumors such as urothelial cancer (VTV; viable tumor volume) to predict overall survival (OS) in patients with metastatic bladder cancer treated with cabozantinib.
  
  
  METHODS
  We compared the relative capabilities of VTV, RECIST, MASS (morphology, attenuation, size, and structure), and Choi criteria, as well as volume measurements, to predict OS using serial follow-up contrast-enhanced CT exams in patients with metastatic urothelial carcinoma. Kaplan-Meier curves and 2-tailed log-rank tests compared OS based on early RECIST 1.1 response against each of the other criteria. A Cox proportional hazards model assessed response at follow-up exams as a time-varying covariate for OS.
  
  
  RESULTS
  We assessed 141 lesions in 55CT scans from 17 patients with urothelial metastasis, comparing VTV, RECIST, MASS, and Choi criteria, and volumetric measurements, for response assessment. Median follow-up was 4.5 months, range was 2-14 months. Only the VTV criteria demonstrated a statistical association with OS (p=0.019; median OS 9.7 vs. 3.5 months).
  
  
  CONCLUSIONS
  This pilot study suggests that VTV is a promising tool for assessing tumor response and predicting OS, using criteria that incorporate tumor volume and density in patients receiving antiangiogenic therapy for urothelial cancer. Larger studies are warranted to further validate these findings.
authors.affiliation: Lead Radiologist for CT, NIH Radiology and Imaging Sciences, 10 Center Drive, Bethesda, MD 20892, USA. Electronic address: Les.folio@nih.gov.
authors.forename: Les Roger
authors.initials: LR
authors.lastname: Folio
authors.affiliation: Johns Hopkins University, Baltimore, MD 21218, USA. Electronic address: evrimbengi@yahoo.com.
authors.forename: Evrim B
authors.initials: EB
authors.lastname: Turkbey
authors.affiliation: Head, Biostatistics and Data Management Section, Office of the Clinical Director, Center for Cancer Research, National Cancer Institute, 9609 Medical Center Drive, Room 2W334, MSC 9716, Bethesda, MD 20892, USA. Electronic address: steinbes@mail.nih.gov.
authors.forename: Seth M
authors.initials: SM
authors.lastname: Steinberg
authors.affiliation: Genitourinary Malignancies Branch, National Cancer Institute, National Institutes of Health, 10 Center Drive, Bethesda, MD 20892, USA.
authors.forename: Andrea B
authors.initials: AB
authors.lastname: Apolo
mesh_terms: D000813:Anilides / Q000627:therapeutic use; D003287:Contrast Media; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D010865:Pilot Projects; D016016:Proportional Hazards Models; D011446:Prospective Studies; D011725:Pyridines / Q000627:therapeutic use; D011856:Radiographic Image Enhancement; D015203:Reproducibility of Results; D012189:Retrospective Studies; D016019:Survival Analysis; D014057:Tomography, X-Ray Computed / Q000379:methods*; D016896:Treatment Outcome; D047368:Tumor Burden; D014571:Urologic Neoplasms / Q000000981:diagnostic imaging* / Q000188:drug therapy / Q000556:secondary; D019459:Urothelium / Q000000981:diagnostic imaging* / Q000473:pathology*
chemical_list: D000813:Anilides; D003287:Contrast Media; D011725:Pyridines; C558660:cabozantinib
keywords: Cancer; Oncology; Segmentation; Tumor burden assessment