The Radiobiological Impact of Dental Root Filling Material in Intensity-Modulated Radiation Therapy (IMRT) in Patients with Nasopharyngeal Carcinoma

Document Type : Original Article (s)

Authors

1 MSc Student, Department of Medical Physics and Engineering, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran

2 Assistant Professor, Department of Medical Physics and Engineering, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran

3 Radiation Oncologist, Department of Radiation-Oncology, Milad Hospital, Isfahan, Iran

4 Associate Professor, Department of Medical Physics, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran

Abstract

Background: Regarding the possibility of perturbation due to the presence of dental root filling material (DFM) in treatment planning of patients with nasopharyngeal cancer, we aimed to evaluate the impact of this material on tumor control probability (TCP) and normal tissue complication probability (NTCP) using dose volume histograms (DVHs) of tumor and organ at risks, measured via treatment planning system.Methods: The optimization process of two intensity modulated radiotherapy (IMRT) techniques was performed by means of Prowess treatment planning system using 7- and 9-field 6-MV photons in two groups of 15 patients with nasopharyngeal cancer, with a difference in the presence or absence of DFM. After preparing DVHs, analysis and comparing of equivalent uniform dose (EUD), TCP, and NTCP were performed using Niemierko’s equivalent.Findings: In 9-field IMRT, there was statically significant decrease in mean EUD, TCP, and conformity index (CI) of tumor in patients with DFM; but there was no significant differences in homogeneity index (HI). Moreover, due to presence of DFM, there was statically significant increase in mean EUD and NTCP of mandible in both 7- and 9-field techniques, and in NTCP of left optic nerve in 9-field IMRT. Although for right eye, there was a statically significant decrease in NTCP by 7-field IMRT technique, due to presence of DFM.Conclusion: The effect of the presence of DFM on IMRT depends on field angles, and leads to significant decrease in TCP target volume, significant increase in NTCP of and EUD mandible and NTCP of left optic nerve, and significant decrease in NTCP of right eye.

Keywords

References

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Journal of Isfahan Medical School
Volume 36, Issue 503 - Serial Number 503
September and October 2019
Pages 1362-1368

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History

  • Receive Date: 17 August 2018
  • Revise Date: 01 November 2024
  • Accept Date: 06 April 2022

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