Analysis of the motion of oropharyngeal tumors and consequences in planning target volume determination.
OBJECTIVE
To determine adequate three-dimensional (3D) margins around the clinical target volume (CTV) of oropharyngeal cancers.


METHODS
The CTV, bounded by implanted markers, was recorded under fluoroscopy in antero-posterior (AP) and lateral view. The peak-to-peak motion was measured in lateral, AP and cranio-caudal (CC) directions.


RESULTS
During swallowing, the mean amplitude of motion measured was 9.4mm (0.9-18.5) and 4.1mm (0.6-11.4) in AP view in the CC and lateral direction, respectively; and 8.6mm (0.5-16.5) and 7.6mm (0.9-14.5) in lateral view in the CC and AP direction, respectively. In the non-swallowing period the motion was 1.5mm (0.3-3.2) and 1mm (0.4-3.6) in AP view in the CC and lateral direction, respectively; and 1.3mm (0.4-3.1) and 1.3mm (0.4-3.4) in lateral view in the CC and AP direction, respectively. This motion was believed to be due to breathing.


CONCLUSIONS
If swallowing can be suppressed during CT acquisition, the contribution to the internal margin for this motion is negligible. Breathing related motion is also believed to be of limited clinical relevance in current practice. However, it might become of importance in future, with further reduction of margins.
Prévost
Jean-Briac
JB
Department of Radiation Oncology, Erasmus MC - Daniel den Hoed, Rotterdam, The Netherlands.
de Boer
Hans
H
Pöll
Johan
J
Voet
Peter
P
Levendag
Peter
P
D002294:Carcinoma, Squamous Cell / Q000473:pathology / Q000601:surgery*; D003679:Deglutition / Q000502:physiology; D005471:Fluoroscopy; D006801:Humans; D009068:Movement; D009959:Oropharyngeal Neoplasms / Q000473:pathology / Q000601:surgery*; D016634:Radiosurgery / Q000295:instrumentation*; D011879:Radiotherapy Dosage; D012119:Respiration