title: Is a Clinical Target Volume (CTV) Necessary in the Treatment of Lung Cancer in the Modern Era Combining 4-D Imaging and Image-guided Radiotherapy (IGRT)?
abstract: OBJECTIVE
  We hypothesized that omission of clinical target volumes (CTV) in lung cancer radiotherapy would not compromise control by determining retrospectively if the addition of a CTV would encompass the site of failure.
  
  
  METHODS
  Stage II-III patients were treated from 2009-2012 with daily cone-beam imaging and a 5 mm planning target volume (PTV) without a CTV. PTVs were expanded 1 cm and termed CTVretro. Recurrences were scored as 1) within the PTV, 2) within CTVretro, or 3) outside the PTV. Locoregional control (LRC), distant control (DC), progression-free survival (PFS), and overall survival (OS) were estimated.
  
  
  RESULTS
  Among 110 patients, Stage IIIA 57%, IIIB 32%, IIA 4%, and IIB 7%. Eighty-six percent of Stage III patients received chemotherapy. Median dose was 70 Gy (45-74 Gy) and fraction size ranged from 1.5-2.7 Gy. Median follow-up was 12 months, median OS was 22 months (95% CI 19-30 months), and LRC at two years was 69%. Fourteen local and eight regional events were scored with two CTVretro failures equating to a two-year CTV failure-free survival of 98%.
  
  
  CONCLUSIONS
  Omission of a 1 cm CTV expansion appears feasible based on only two events among 110 patients and should be considered in radiation planning.
authors.affiliation: Radiation Oncology, Wake Forest School of Medicine.
authors.forename: Jeremy M
authors.initials: JM
authors.lastname: Kilburn
authors.affiliation: Radiation Oncology, Wake Forest School of Medicine.
authors.forename: John T
authors.initials: JT
authors.lastname: Lucas
authors.affiliation: Radiation Oncology, Wake Forest School of Medicine.
authors.forename: Michael H
authors.initials: MH
authors.lastname: Soike
authors.affiliation: Radiation Oncology, Wake Forest School of Medicine.
authors.forename: Diandra N
authors.initials: DN
authors.lastname: Ayala-Peacock
authors.affiliation: Radiation Oncology, Wake Forest School of Medicine.
authors.forename: Arthur W
authors.initials: AW
authors.lastname: Blackstock
authors.affiliation: Radiation Oncology, Wake Forest School of Medicine.
authors.forename: William H
authors.initials: WH
authors.lastname: Hinson
authors.affiliation: Radiation Oncology, Wake Forest School of Medicine.
authors.forename: Michael T
authors.initials: MT
authors.lastname: Munley
authors.affiliation: Medicine, Division of Hematology/Oncology, Wake Forest School of Medicine.
authors.forename: William J
authors.initials: WJ
authors.lastname: Petty
authors.affiliation: Radiation Medicine and Applied Sciences, UCSD School of Medicine.
authors.forename: James J
authors.initials: JJ
authors.lastname: Urbanic
keywords: clinical target volume; image-guided radiation therapy; lung cancer; non-small cell lung cancers (nsclc); radiation treatment planning