title: Should patient setup in lung cancer be based on the primary tumor? An analysis of tumor coverage and normal tissue dose using repeated positron emission tomography/computed tomography imaging.
abstract: OBJECTIVE
  Evaluation of the dose distribution for lung cancer patients using a patient setup procedure based on the bony anatomy or the primary tumor.
  
  
  METHODS
  For 39 patients with non-small-cell lung cancer, the planning fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) scan was registered to a repeated FDG-PET/CT scan made in the second week of treatment. Two patient setup methods were analyzed based on the bony anatomy or the primary tumor. The original treatment plan was copied to the repeated scan, and target and normal tissue structures were delineated. Dose distributions were analyzed using dose-volume histograms for the primary tumor, lymph nodes, lungs, and spinal cord.
  
  
  RESULTS
  One patient showed decreased dose coverage of the primary tumor caused by progressive disease and required replanning to achieve adequate coverage. For the other patients, the minimum dose to the primary tumor did not significantly deviate from the planned dose: -0.2 ± 1.7% (p = 0.71) and -0.1 ± 1.7% (p = 0.85) for the bony anatomy setup and the primary tumor setup, respectively. For patients (n = 31) with nodal involvement, 10% showed a decrease in minimum dose larger than 5% for the bony anatomy setup and 13% for the primary tumor setup. The mean lung dose exceeded the maximum allowed 20 Gy in 21% of the patients for the bony anatomy setup and in 13% for the primary tumor setup, whereas for the spinal cord this occurred in 10% and 13% of the patients, respectively.
  
  
  CONCLUSIONS
  In 10% and 13% of patients with nodal involvement, setup based on bony anatomy or primary tumor, respectively, led to important dose deviations in nodal target volumes. Overdosage of critical structures occurred in 10-20% of the patients. In cases of progressive disease, repeated imaging revealed underdosage of the primary tumor. Development of practical ways for setup procedures based on repeated high-quality imaging of all tumor sites during radiotherapy should therefore be an important research focus.
authors.affiliation: Department of Radiation Oncology, MAASTRO, GROW-School for Oncology and Developmental Biology, Maastricht University Medical Centre, Maastricht, The Netherlands. wouter.vanelmpt@maastro.nl
authors.forename: Wouter
authors.initials: W
authors.lastname: van Elmpt
authors.forename: Michel
authors.initials: M
authors.lastname: Öllers
authors.forename: Philippe
authors.initials: P
authors.lastname: Lambin
authors.forename: Dirk
authors.initials: D
authors.lastname: De Ruysscher
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D059925:Anatomic Landmarks / Q000000981:diagnostic imaging*; D001842:Bone and Bones / Q000000981:diagnostic imaging; D002289:Carcinoma, Non-Small-Cell Lung / Q000000981:diagnostic imaging* / Q000188:drug therapy / Q000532:radiotherapy; D018450:Disease Progression; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D060828:Induction Chemotherapy / Q000379:methods; D008168:Lung / Q000000981:diagnostic imaging; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000188:drug therapy / Q000532:radiotherapy; D008198:Lymph Nodes / Q000000981:diagnostic imaging; D008297:Male; D008482:Mediastinum / Q000000981:diagnostic imaging; D008875:Middle Aged; D064847:Multimodal Imaging / Q000379:methods*; D058958:Organs at Risk / Q000000981:diagnostic imaging*; D049268:Positron-Emission Tomography; D011446:Prospective Studies; D019275:Radiopharmaceuticals; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D055752:Small Cell Lung Carcinoma / Q000000981:diagnostic imaging* / Q000188:drug therapy / Q000532:radiotherapy; D013116:Spinal Cord / Q000000981:diagnostic imaging; D014057:Tomography, X-Ray Computed; D047368:Tumor Burden
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18