Precision required for dose-escalated treatment of spinal metastases and implications for image-guided radiation therapy (IGRT).
BACKGROUND
To evaluate the precision required in dose-escalated IMRT treatment of spinal metastases and paraspinal tumors.


METHODS
In IMRT treatment plans of nine patients with spinal metastases (n=7) and paraspinal tumors (n=2) translational patient positioning errors (0-10mm) and rotational errors (0-7.5 degrees ) were simulated. The dose to the spinal cord (D5(spine)) resulting from these simulations was evaluated and NTCP for spinal cord necrosis was calculated. All patient set-up errors observed during treatment were simulated and the influence on D5(spine) was investigated.


RESULTS
To keep the dose distribution to the spinal cord within +/-5% (+/-10%) of the prescribed dose, maximum tolerable errors of 1mm (2mm) in the transversal plane, 4mm (7mm) in superior-inferior direction and maximum rotations of 3.5 degrees (5 degrees ) were calculated on average. The translational and rotational component of clinically observed set-up errors increased D5(spine) by 23+/-14% and 3+/-2% on average, respectively.


CONCLUSIONS
Steep dose gradients of IMRT planning require very high precision. In selected patients correction of both translational and rotational errors may be beneficial.
Guckenberger
Matthias
M
Department of Radiation Oncology, University of Wuerzburg, Wuerzburg, Germany. guckenberg_m@klinik.uni-wuerzburg.de
Meyer
Juergen
J
Wilbert
Juergen
J
Baier
Kurt
K
Bratengeier
Klaus
K
Vordermark
Dirk
D
Flentje
Michael
M
D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D005069:Evaluation Studies as Topic; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011829:Radiation Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D020266:Radiotherapy, Conformal; D013125:Spinal Neoplasms / Q000532:radiotherapy* / Q000556:secondary