title: Intra-patient variability of tumor volume and tumor motion during conventionally fractionated radiotherapy for locally advanced non-small-cell lung cancer: a prospective clinical study.
abstract: OBJECTIVE
  The aim of this study was to investigate the change in tumor volume, motion, and breathing frequency during a course of radiotherapy, for locally advanced non-small-cell lung cancer.
  
  
  METHODS
  A total of 23 patients underwent computed tomography-positron emission tomography (CT-PET) and respiration correlated CT scans before treatment, which was repeated in the first and second weeks after the start of radiotherapy. Patients were treated with an accelerated fractionation schedule, 1.8 Gy twice a day, with a total tumor dose depending on preset dose constraints for the lungs and spinal cord.
  
  
  RESULTS
  A striking heterogeneity of tumor volume changes was observed at all time points. In some patients the volume decreased >30% (3/23), whereas in others the volume increased >30% (4/24); but for the majority of patients (16/23), the tumor volume changed only slightly (<30%). No significant changes in average tumor motion or breathing frequencies were observed during treatment. Although a number of changes in individual tumor motion were seen, only in 1 patient would this have led to an increase of the internal margin >1 mm in 1 direction, 1 week after the start of treatment, and in 3 patients for 1 direction, 2 weeks after the start of the treatment.
  
  
  CONCLUSIONS
  In this patients in this study, a large variability in changes in tumor volume was observed. This underscores the need for repeated imaging during the course of radiotherapy. However, the changes in tumor motion are small, which indicates that repeated respiration correlated CT does not appear to be necessary.
authors.affiliation: Department of Radiation Oncology (MAASTRO), GROW, University Hospital Maastricht, Maastricht, The Netherlands. geert.bosmans@maastro.nl
authors.forename: Geert
authors.initials: G
authors.lastname: Bosmans
authors.forename: Angela
authors.initials: A
authors.lastname: van Baardwijk
authors.forename: André
authors.initials: A
authors.lastname: Dekker
authors.forename: Michel
authors.initials: M
authors.lastname: Ollers
authors.forename: Liesbeth
authors.initials: L
authors.lastname: Boersma
authors.forename: André
authors.initials: A
authors.lastname: Minken
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; D002289:Carcinoma, Non-Small-Cell Lung / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D008297:Male; D008875:Middle Aged; D009068:Movement; D049268:Positron-Emission Tomography; D011446:Prospective Studies; D011879:Radiotherapy Dosage; D012119:Respiration; D014057:Tomography, X-Ray Computed