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Radiation-induced biological changes of neural structures in the base of the skull tumours

Published online by Cambridge University Press:  18 January 2017

C. Gh. Buzea*
Affiliation:
Regional Institute of Oncology, Iasi, Romania
C. Mirestean
Affiliation:
Regional Institute of Oncology, Iasi, Romania
Irina Butuc
Affiliation:
Regional Institute of Oncology, Iasi, Romania
A. Zara
Affiliation:
Regional Institute of Oncology, Iasi, Romania
D. T. Iancu
Affiliation:
‘Grigore T. Popa’, University of Medicine and Pharmacy, Iasi, Romania
*
Correspondence to: C. Gh. Buzea, Regional Institute of Oncology, Henry Mathias Berthelot 2–4, Iasi, Romania Tel: +40 753 675353. Fax: +40 232 231132. E-mail: calinb2003@yahoo.com

Abstract

Background and purpose

The aim of this paper is to compare neural induced changes in three-dimensional conformal radiotherapy (3D-CRT) versus intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) for nasopharyngeal cancers.

Materials and methods

Radiotherapy plans for 10 patients with nasopharyngeal cancer stages III and IV were prospectively developed for 3D-CRT, IMRT and VMAT using Varian Eclipse planning system. The same radiation therapist carried out all planning and the same clinical dosimetric constraints were used. Normal tissue complication probabilities were calculated.

Results

The mean planning target volume’s (PTVs) conformity index (CI) for 3D-CRT was 1·424, for IMRT 1·1, and for VMAT 1·081. The PTV homogeneity (HI) index was 0·204 for 3D-CRT, 0·124 for IMRT and 0·153 for VMAT. Normal tissue complication probabilities gave complex results for 3D-CRT, IMRT and VMAT and are analysed in detail in this paper. The mean monitor units were 95 (range 9–180) for 3D-CRT; 165 (range 52–277) for IMRT; and 331 (range 167–494) for VMAT (p<0·05).

Conclusions

VMAT is associated with similar dosimetric advantages as IMRT over 3D-CRT for nasopharyngeal cancer. VMAT is associated with faster delivery times and greater number of mean monitor units than IMRT. Brain radionecrosis severity and risk, in the past, have been underestimated. By improving the life expectancy of patients with nasopharyngeal cancer to ensure maintenance of the neural structures, recommended dose limits should be considered as a first degree priority (as the spinal cord, brainstem, etc.) when IMRT and VMAT plans are implemented.

Information

Type
Original Articles
Copyright
© Cambridge University Press 2017 

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