Consequences of additional use of PET information for target volume delineation and radiotherapy dose distribution for esophageal cancer.
OBJECTIVE
To determine the consequences of target volume (TV) modifications, based on the additional use of PET information, on radiation planning, assuming PET/CT-imaging represents the true extent of the tumour.


METHODS
For 21 patients with esophageal cancer, two separate TV's were retrospectively defined based on CT (CT-TV) and co-registered PET/CT images (PET/CT-TV). Two 3D-CRT plans (prescribed dose 50.4 Gy) were constructed to cover the corresponding TV's. Subsequently, these plans were compared for target coverage, normal tissue dose-volume histograms and the corresponding normal tissue complication probability (NTCP) values.


RESULTS
The addition of PET led to the modification of CT-TV with at least 10% in 12 of 21 patients (57%) (reduction in 9, enlargement in 3). PET/CT-TV was inadequately covered by the CT-based treatment plan in 8 patients (36%). Treatment plan modifications resulted in significant changes (p<0.05) in dose distributions to heart and lungs. Corresponding changes in NTCP values ranged from -3% to +2% for radiation pneumonitis and from -0.2% to +1.2% for cardiac mortality.


CONCLUSIONS
This study demonstrated that TV's based on CT might exclude PET-avid disease. Consequences are under dosing and thereby possibly ineffective treatment. Moreover, the addition of PET in radiation planning might result in clinical important changes in NTCP.
Muijs
Christina T
CT
Department of Radiation Oncology, University Medical Centre Groningen/University of Groningen, Groningen, The Netherlands. c.t.muijs@rt.umcg.nl
Schreurs
Liesbeth M
LM
Busz
Dianne M
DM
Beukema
Jannet C
JC
van der Borden
Arnout J
AJ
Pruim
Jan
J
Van der Jagt
Eric J
EJ
Plukker
John Th
JT
Langendijk
Johannes A
JA
D000230:Adenocarcinoma / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D000368:Aged; D002294:Carcinoma, Squamous Cell / Q000000981:diagnostic imaging* / Q000532:radiotherapy; D004938:Esophageal Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D020266:Radiotherapy, Conformal; D014057:Tomography, X-Ray Computed
D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18