Correlation of contouring variation with modeled outcome for conformal non-small cell lung cancer radiotherapy.
OBJECTIVE
Contouring variation is a well know uncertainty in modern radiotherapy. This study investigates the relationship between contouring variation, tumor control probability (TCP) and equivalent uniform dose (EUD) for conformal non-small cell lung cancer (NSCLC) radiotherapy.


METHODS
Seven patients were retrospectively recruited to the study and multiple PTV contours were generated based on CT and PET imaging by three observers. Plans were created for each PTV volume. Volumes were analyzed geometrically using volume, location, dimension and conformity index (CI). Radiobiological plan analysis consisted of two TCP models and EUD. Spearman's correlation coefficient (ρ) was used to quantify the association between geometric variation and radiobiological metrics.


RESULTS
The variation in CI and TCP for the study was 0.66-0.90% and 0.19-0.68%. Changes in lateral dimension and volume were significantly correlated with TCP and EUD with an average ρ of -0.49 and 0.43 (p<0.01) respectively.


CONCLUSIONS
TCP and geometric contour variation show significant correlation. This correlation was most significant for changes in lateral dimensions of PTV volumes. This association may be used in the assessment of contouring protocol violations in multicenter clinical trials and aid in the design of future contouring studies.
Liverpool and Macarthur Cancer Therapy Centres, Australia; Centre for Medical Radiation Physics, University of Wollongong, Australia; Ingham Institute of Applied Medical Research, Australia. Electronic address: michael.jameson@sswahs.nsw.gov.au.
Michael G
MG
Jameson
Liverpool and Macarthur Cancer Therapy Centres, Australia; Ingham Institute of Applied Medical Research, Australia; South Western Sydney Clinical School, University of New South Wales, Australia.
Shivani
S
Kumar
Liverpool and Macarthur Cancer Therapy Centres, Australia; Ingham Institute of Applied Medical Research, Australia; South Western Sydney Clinical School, University of New South Wales, Australia.
Shalini K
SK
Vinod
Centre for Medical Radiation Physics, University of Wollongong, Australia.
Peter E
PE
Metcalfe
Liverpool and Macarthur Cancer Therapy Centres, Australia; Centre for Medical Radiation Physics, University of Wollongong, Australia; Ingham Institute of Applied Medical Research, Australia; South Western Sydney Clinical School, University of New South Wales, Australia; Institute of Medical Physics, School of Physics, University of Sydney, Australia.
Lois C
LC
Holloway
D000328:Adult; D059925:Anatomic Landmarks / Q000000981:diagnostic imaging; D002289:Carcinoma, Non-Small-Cell Lung / Q000175:diagnosis* / Q000532:radiotherapy*; D003287:Contrast Media; D005260:Female; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging; D008175:Lung Neoplasms / Q000175:diagnosis* / Q000532:radiotherapy*; D008297:Male; D008875:Middle Aged; D008962:Models, Theoretical; D015588:Observer Variation; D049268:Positron-Emission Tomography / Q000379:methods; D011856:Radiographic Image Enhancement / Q000379:methods; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D020266:Radiotherapy, Conformal / Q000379:methods*; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000379:methods; D016896:Treatment Outcome
D003287:Contrast Media
Contouring variation; EUD; Lung cancer; TCP