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Clinical dosimetry optimization in spinal metastases

Published online by Cambridge University Press:  01 March 2009

P. Pedrosa ,
C. Lucena  and
I.J. Sainz
P. Pedrosa*
Affiliation:
Unidad de Gestión Clínica de Oncohematología, Hospital Virgen de la Victoria, Málaga, Spain
C. Lucena
Affiliation:
Unidad de Gestión Clínica de Oncohematología, Hospital Virgen de la Victoria, Málaga, Spain
I.J. Sainz
Affiliation:
Unidad de Gestión Clínica de Oncohematología, Hospital Virgen de la Victoria, Málaga, Spain
*
Correspondence to: P. Pedrosa, Unidad de Gestión Clínica de Oncohematología, Hospital Virgen de la Victoria, Campus de Teatinos s/n 29010 Málaga, Spain. E-mail: ppedrosagarcia@hotmail.com
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Abstract

Introduction: Radiotherapy is commonly used to treat spinal metastases. The aim of this study was to compare conventional dosimetry (posterior–anterior fields) with an optimized three-dimensional conformal plan (using oblique fields).

Material and Methods: Fifteen patients were selected, and split into three groups of five based on tumour localization: cervical, dorsal and lumbar. Reference planning comprised of two fields: anterior–posterior. The planning target volume (PTV) was covered with 90% of the prescribed doses, minimizing anterior field weight and not exceeding 120%. The alternative consisted of three fields: two oblique posterior fields with wedge and anterior field. The PTV was covered with 95% of the prescription dose, minimizing the anterior field weight with 107% of overdose as a limit. The patient received 8 Gy in one fraction; retreatment with an additional fraction was feasible, safe and effective if persistent or recurrent bone pain was present. Five fractions of 4 Gy were used for cervical cases. To consider the future patients toxicity we evaluated the mean dose, V90 and V70 parameters in each plan.

Results: Dosimetric parameters of organs at risk were not significantly different from one trial to another. The optimized plan followed ICRU criteria, reaching PTV coverage of 95–107% range of the prescription dose. In the conventional plan, high dose had to be accepted to obtain 90% of coverage in the target.

Conclusions: In contrast with the anterior–posterior configuration, oblique fields improve dose conformity and limit high dose all of the body except the spinal cord.

Keywords

Metastases spinal cord compressionclinical dosimetrytreatment optimization
Type
Original Article
Information
Journal of Radiotherapy in Practice , Volume 8 , Issue 1 , March 2009 , pp. 35 - 40
Copyright
Copyright © Cambridge University Press 2009

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