Reproducibility of "intelligent" contouring of gross tumor volume in non-small-cell lung cancer on PET/CT images using a standardized visual method.
OBJECTIVE
Positron emission tomography/computed tomography (PET/CT) is increasingly used for delineating gross tumor volume (GTV) in non-small-cell lung cancer (NSCLC). The methodology for contouring tumor margins remains controversial. We developed a rigorous visual protocol for contouring GTV that uses all available clinical information and studied its reproducibility in patients from a prospective PET/CT planning trial.


METHODS
Planning PET/CT scans from 6 consecutive patients were selected. Six "observers" (two radiation oncologists, two nuclear medicine physicians, and two radiologists) contoured GTVs for each patient using a predefined protocol and subsequently recontoured 2 patients. For the estimated GTVs and axial distances, least-squares means for each observer and for each case were calculated and compared, using the F test and pairwise t-tests. In five cases, tumor margins were also autocontoured using standardized uptake value (SUV) cutoffs of 2.5 and 3.5 and 40% SUV(max).


RESULTS
The magnitude of variation between observers was small relative to the mean (coefficient of variation [CV] = 3%), and the total variation (intraclass correlation coefficient [ICC] = 3%). For estimation of superior/inferior (SI), left/right (LR), and anterior/posterior (AP) borders of the GTV, differences between observers were also small (AP, CV = 2%, ICC = 0.4%; LR, CV = 6%, ICC = 2%; SI, CV 4%, ICC = 2%). GTVs autocontoured generated using SUV 2.5, 3.5, and 40% SUV(max) differed widely in each case. An SUV contour of 2.5 was most closely correlated with the mean GTV defined by the human observers.


CONCLUSIONS
Observer variation contributed little to total variation in the GTV and axial distances. A visual contouring protocol gave reproducible results for contouring GTV in NSCLC.
Bayne
Michael
M
Dorset Cancer Centre, Poole Hospital, Poole, Dorset, UK.
Hicks
Rodney J
RJ
Everitt
Sarah
S
Fimmell
Natalie
N
Ball
David
D
Reynolds
John
J
Lau
Eddie
E
Pitman
Alex
A
Ware
Robert
R
MacManus
Michael
M
D002289:Carcinoma, Non-Small-Cell Lung / Q000000981:diagnostic imaging* / Q000473:pathology; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology; D009683:Nuclear Medicine / Q000592:standards; D015588:Observer Variation; D049268:Positron-Emission Tomography / Q000379:methods / Q000592:standards; D011446:Prospective Studies; D018787:Radiation Oncology / Q000592:standards; D011871:Radiology / Q000592:standards; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D018401:Sample Size; D014057:Tomography, X-Ray Computed / Q000379:methods / Q000592:standards; D047368:Tumor Burden
D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18