Prospective randomized double-blind pilot study of site-specific consensus atlas implementation for rectal cancer target volume delineation in the cooperative group setting.
OBJECTIVE
Variations in target volume delineation represent a significant hurdle in clinical trials involving conformal radiotherapy. We sought to determine the effect of a consensus guideline-based visual atlas on contouring the target volumes.


METHODS
A representative case was contoured (Scan 1) by 14 physician observers and a reference expert with and without target volume delineation instructions derived from a proposed rectal cancer clinical trial involving conformal radiotherapy. The gross tumor volume (GTV), and two clinical target volumes (CTVA, including the internal iliac, presacral, and perirectal nodes, and CTVB, which included the external iliac nodes) were contoured. The observers were randomly assigned to receipt (Group A) or nonreceipt (Group B) of a consensus guideline and atlas for anorectal cancers and then instructed to recontour the same case/images (Scan 2). Observer variation was analyzed volumetrically using the conformation number (CN, where CN = 1 equals total agreement).


RESULTS
Of 14 evaluable contour sets (1 expert and 7 Group A and 6 Group B observers), greater agreement was found for the GTV (mean CN, 0.75) than for the CTVs (mean CN, 0.46-0.65). Atlas exposure for Group A led to significantly increased interobserver agreement for CTVA (mean initial CN, 0.68, after atlas use, 0.76; p = .03) and increased agreement with the expert reference (initial mean CN, 0.58; after atlas use, 0.69; p = .02). For the GTV and CTVB, neither the interobserver nor the expert agreement was altered after atlas exposure.


CONCLUSIONS
Consensus guideline atlas implementation resulted in a detectable difference in interobserver agreement and a greater approximation of expert volumes for the CTVA but not for the GTV or CTVB in the specified case. Visual atlas inclusion should be considered as a feature in future clinical trials incorporating conformal RT.
Fuller
Clifton D
CD
Department of Radiation Oncology, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA. fullercd@uthscsa.edu
Nijkamp
Jasper
J
Duppen
Joop C
JC
Rasch
Coen R N
CR
Thomas
Charles R
CR
Wang
Samuel J
SJ
Okunieff
Paul
P
Jones
William E
WE
Baseman
Daniel
D
Patel
Shilpen
S
Demandante
Carlo G N
CG
Harris
Anna M
AM
Smith
Benjamin D
BD
Katz
Alan W
AW
McGann
Camille
C
Harper
Jennifer L
JL
Chang
Daniel T
DT
Smalley
Stephen
S
Marshall
David T
DT
Goodman
Karyn A
KA
Papanikolaou
Niko
N
Kachnic
Lisa A
LA
D004311:Double-Blind Method; D006801:Humans; D008488:Medical Illustration; D015588:Observer Variation; D010865:Pilot Projects; D011446:Prospective Studies; D018787:Radiation Oncology; D011859:Radiography; D020266:Radiotherapy, Conformal / Q000379:methods; D012004:Rectal Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000532:radiotherapy; D047368:Tumor Burden
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