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Dose analysis of boost treatment to parapharyngeal space of nasopharyngeal carcinoma using three-dimensional conformal radiotherapy

Published online by Cambridge University Press:  21 August 2006

Vincent W C Wu ,
Candy S C Tsang ,
Freddy H K Mak ,
Joe C H Chan ,
Kenneth M W Leung  and
H W Leung
Vincent W C Wu
Affiliation:
Department of Optometry & Radiography, Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong
Candy S C Tsang
Affiliation:
Department of Optometry & Radiography, Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong
Freddy H K Mak
Affiliation:
Department of Optometry & Radiography, Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong
Joe C H Chan
Affiliation:
Department of Optometry & Radiography, Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong
Kenneth M W Leung
Affiliation:
Department of Optometry & Radiography, Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong
H W Leung
Affiliation:
Department of Optometry & Radiography, Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong
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Abstract

Nasopharyngeal carcinoma (NPC) patients with parapharyngeal space (PPS) involvement are routinely given boost irradiation in Hong Kong. The current technique that employs a single field has many limitations in terms of dose distribution. This study is aimed to compare the dose distribution between the newly designed 3-dimensional conformal radiotherapy (3DCRT) and conventional techniques for the boost treatment of PPS so as to determine the more optimal treatment.

Fifteen NPC patients with unilateral PPS involvement were recruited. Their CT images were loaded into the FOCUS planning system for treatment planning. The planning target volume (PTV) and seven organs at risk (OARs) including the spinal cord, brain stem, optic chiasm, mandible, temporal lobe, temporo-mandibular (TM) joint and lens were outlined for dose assessment. The conventional and 3DCRT plans were then generated for each patient and the dose distributions were compared using dose parameters derived from the dose volume histograms (DVHs).

The 3DCRT technique provides better target coverage and significantly better dose to the planning target volume than the conventional technique. The 3DCRT treatment plans gives better sparing of the ipsilateral TM joints, mandible and lens, but it is less effective to spare spinal cord, brain stem, optic chiasm and temporal lobe. Nevertheless, the total doses to these OARs remain within the clinically defined thresholds and are clinically acceptable.

Keywords

nasopharyngeal carcinoma3D conformal radiotherapyparapharyngealspacedosimetric assessment
Type
Original Article
Information
Journal of Radiotherapy in Practice , Volume 2 , Issue 3 , September 2000 , pp. 139 - 145
Copyright
2000 Cambridge University Press

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