The delineation of target volumes for radiotherapy of lung cancer patients.
OBJECTIVE
Differences in the delineation of the gross target volume (GTV) and planning target volume (PTV) in patients with non-small-cell lung cancer are considerable. The focus of this work is on the analysis of observer-related reasons while controlling for other variables.


METHODS
In three consecutive patients, eighteen physicians from fourteen different departments delineated the GTV and PTV in CT-slices using a detailed instruction for target delineation. Differences in the volumes, the delineated anatomic lymph node compartments and differences in every delineated pixel of the contoured volumes in the CT-slices (pixel-by-pixel-analysis) were evaluated for different groups: ten radiation oncologists from ten departments (ROs), four haematologic oncologists and chest physicians from four departments (HOs) and five radiation oncologists from one department (RO1D).


RESULTS
Agreement (overlap > or = 70% of the contoured pixels) for the GTV and PTV delineation was found in 16.3% and 23.7% (ROs), 30.4% and 38.6% (HOs) and 32.8% and 35.9% (RO1D), respectively.


CONCLUSIONS
A large interobserver variability in the PTV and much more in the GTV delineation were observed in spite of a detailed instruction for delineation. The variability was smallest for group ROID where due to repeated discussions and uniform teaching a better agreement was achieved.
Vorwerk
Hilke
H
Department of Radiotherapy and Radiooncology, University Hospital Göttingen, Robert-Koch-Strasse, Germany. h.vorwerk@med.uni-goettingen.de
Beckmann
Gabriele
G
Bremer
Michael
M
Degen
Maria
M
Dietl
Barbara
B
Fietkau
Rainer
R
Gsänger
Tammo
T
Hermann
Robert Michael
RM
Alfred Herrmann
Markus Karl
MK
Höller
Ulrike
U
van Kampen
Michael
M
Körber
Wolfgang
W
Maier
Burkhard
B
Martin
Thomas
T
Metz
Michael
M
Richter
Ronald
R
Siekmeyer
Birgit
B
Steder
Martin
M
Wagner
Daniela
D
Hess
Clemens Friedrich
CF
Weiss
Elisabeth
E
Christiansen
Hans
H