The reasons for discrepancies in target volume delineation : a SASRO study on head-and-neck and prostate cancers.
OBJECTIVE
To understand the reasons for differences in the delineation of target volumes between physicians.


METHODS
18 Swiss radiooncology centers were invited to delineate volumes for one prostate and one head-and-neck case. In addition, a questionnaire was sent to evaluate the differences in the volume definition (GTV [gross tumor volume], CTV [clinical target volume], PTV [planning target volume]), the various estimated margins, and the nodes at risk. Coherence between drawn and stated margins by centers was calculated. The questionnaire also included a nonspecific series of questions regarding planning methods in each institution.


RESULTS
Fairly large differences in the drawn volumes were seen between the centers in both cases and also in the definition of volumes. Correlation between drawn and stated margins was fair in the prostate case and poor in the head-and-neck case. The questionnaire revealed important differences in the planning methods between centers.


CONCLUSIONS
These large differences could be explained by (1) a variable knowledge/interpretation of ICRU definitions, (2) variable interpretations of the potential microscopic extent, (3) difficulties in GTV identification, (4) differences in the concept, and (5) incoherence between theory (i.e., stated margins) and practice (i.e., drawn margins).
Jeanneret-Sozzi
Wendy
W
Department of Radiation Oncology, University Hospital of Lausanne, Lausanne, Switzerland.
Moeckli
Raphaël
R
Valley
Jean-François
JF
Zouhair
Abderrahim
A
Ozsahin
Esat Mahmut
EM
Mirimanoff
René-Olivier
RO
D000230:Adenocarcinoma / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*; D000368:Aged; D016251:CD-ROM; D002294:Carcinoma, Squamous Cell / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*; D006258:Head and Neck Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*; D006801:Humans; D008198:Lymph Nodes / Q000473:pathology; D008297:Male; D009367:Neoplasm Staging; D015588:Observer Variation; D011467:Prostate / Q000473:pathology; D017430:Prostate-Specific Antigen / Q000097:blood; D011471:Prostatic Neoplasms / Q000097:blood / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*; D011880:Radiotherapy Planning, Computer-Assisted; D011795:Surveys and Questionnaires; D014057:Tomography, X-Ray Computed; D014059:Tongue / Q000473:pathology; D014062:Tongue Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*
D017430:Prostate-Specific Antigen