title: Modeling of non-small cell lung cancer volume changes during CT-based image guided radiotherapy: patterns observed and clinical implications.
abstract: Background. To characterize the lung tumor volume response during conventional and hypofractionated radiotherapy (RT) based on diagnostic quality CT images prior to each treatment fraction. Methods. Out of 26 consecutive patients who had received CT-on-rails IGRT to the lung from 2004 to 2008, 18 were selected because they had lung lesions that could be easily distinguished. The time course of the tumor volume for each patient was individually analyzed using a computer program. Results. The model fits of group L (conventional fractionation) patients were very close to experimental data, with a median Δ% (average percent difference between data and fit) of 5.1% (range 3.5-10.2%). The fits obtained in group S (hypofractionation) patients were generally good, with a median Δ% of 7.2% (range 3.7-23.9%) for the best fitting model. Four types of tumor responses were observed-Type A: "high" kill and "slow" dying rate; Type B: "high" kill and "fast" dying rate; Type C: "low" kill and "slow" dying rate; and Type D: "low" kill and "fast" dying rate. Conclusions. The models used in this study performed well in fitting the available dataset. The models provided useful insights into the possible underlying mechanisms responsible for the RT tumor volume response.
authors.affiliation: Department of Radiation Oncology, Washington University School of Medicine, 4921 Parkview Place, Campus Box 8224, St. Louis, MO, 63110, USA.
authors.forename: Hiram A
authors.initials: HA
authors.lastname: Gay
authors.forename: Quendella Q
authors.initials: QQ
authors.lastname: Taylor
authors.forename: Fumika
authors.initials: F
authors.lastname: Kiriyama
authors.forename: Geoffrey T
authors.initials: GT
authors.lastname: Dieck
authors.forename: Todd
authors.initials: T
authors.lastname: Jenkins
authors.forename: Paul
authors.initials: P
authors.lastname: Walker
authors.forename: Ron R
authors.initials: RR
authors.lastname: Allison
authors.forename: Paolo
authors.initials: P
authors.lastname: Ubezio
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002289:Carcinoma, Non-Small-Cell Lung / Q000000981:diagnostic imaging* / Q000473:pathology / Q000532:radiotherapy*; D049109:Cell Proliferation / Q000528:radiation effects; D003198:Computer Simulation; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000532:radiotherapy*; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D011836:Radiation Tolerance; D061089:Radiotherapy, Image-Guided / Q000706:statistics & numerical data; D014057:Tomography, X-Ray Computed / Q000706:statistics & numerical data