title: Using fluorodeoxyglucose positron emission tomography to assess tumor volume during radiotherapy for non-small-cell lung cancer and its potential impact on adaptive dose escalation and normal tissue sparing.
abstract: OBJECTIVE
  To quantify changes in fluorodeoxyglucose (FDG)-avid tumor volume on positron emission tomography/computed tomography (PET/CT) during the course of radiation therapy and examine its potential use in adaptive radiotherapy for tumor dose escalation or normal tissue sparing in patients with non-small-cell lung cancer (NSCLC).
  
  
  METHODS
  As part of a pilot study, patients with Stage I-III NSCLC underwent FDG-PET/CT before radiotherapy (RT) and in mid-RT (after 40-50 Gy). Gross tumor volumes were contoured on CT and PET scans obtained before and during RT. Three-dimensional conformal RT plans were generated for each patient, first using only pretreatment CT scans. Mid-RT PET volumes were then used to design boost fields.
  
  
  RESULTS
  Fourteen patients with FDG-avid tumors were assessed. Two patients had a complete metabolic response, and 2 patients had slightly increased FDG uptake in the adjacent lung tissue. Mid-RT PET scans were useful in the 10 remaining patients. Mean decreases in CT and PET tumor volumes were 26% (range, +15% to -75%) and 44% (range, +10% to -100%), respectively. Designing boosts based on mid-RT PET allowed for a meaningful dose escalation of 30-102 Gy (mean, 58 Gy) or a reduction in normal tissue complication probability (NTCP) of 0.4-3% (mean, 2%) in 5 of 6 patients with smaller yet residual tumor volumes.
  
  
  CONCLUSIONS
  Tumor metabolic activity and volume can change significantly after 40-50 Gy of RT. Using mid-RT PET volumes, tumor dose can be significantly escalated or NTCP reduced. Clinical studies evaluating patient outcome after PET-based adaptive RT are ongoing.
authors.affiliation: Department of Radiation Oncology, University of Michigan, Ann Arbor, MI 48109, USA.
authors.forename: Mary
authors.initials: M
authors.lastname: Feng
authors.forename: Feng-Ming
authors.initials: FM
authors.lastname: Kong
authors.forename: Milton
authors.initials: M
authors.lastname: Gross
authors.forename: Shaneli
authors.initials: S
authors.lastname: Fernando
authors.forename: James A
authors.initials: JA
authors.lastname: Hayman
authors.forename: Randall K
authors.initials: RK
authors.lastname: Ten Haken
mesh_terms: D002289:Carcinoma, Non-Small-Cell Lung / Q000000981:diagnostic imaging / Q000378:metabolism / Q000473:pathology / Q000532:radiotherapy; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging / Q000378:metabolism / Q000473:pathology / Q000532:radiotherapy; D010865:Pilot Projects; D049268:Positron-Emission Tomography / Q000379:methods; D011446:Prospective Studies; D011832:Radiation Injuries / Q000517:prevention & control; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D011879:Radiotherapy Dosage; D014057:Tomography, X-Ray Computed; D047368:Tumor Burden
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18