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The choice of statistical methods for comparisons of dosimetric data in radiotherapy

  • Chaikh, Abdulhamid University Joseph Fourier, Grenoble, France - Department of Radiation Oncology and Medical physics, Grenoble University Hospital, Grenoble, France
  • Giraud, Jean-Yves University Joseph Fourier, Grenoble, France - Department of Radiation Oncology and Medical physics, Grenoble University Hospital, Grenoble, France
  • Perrin, Emmanuel University Claude Bernard Lyon 1, Villeurbanne, France
  • Bresciani, Jean-Pierre Department of Medicine, University of Fribourg, Switzerland - LPNC, CNRS & Grenoble-Alpes University, Grenoble, France
  • Balosso, Jacques University Joseph Fourier, Grenoble, France - Department of Radiation Oncology and Medical physics, Grenoble University Hospital, Grenoble, France
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    18.09.2014
Published in:
  • Radiation Oncology. - 2014, vol. 9, no. 1, p. 205
Statistical methods
Dose
Radiotherapy
English Purpose: Novel irradiation techniques are continuously introduced in radiotherapy to optimize the accuracy, the security and the clinical outcome of treatments. These changes could raise the question of discontinuity in dosimetric presentation and the subsequent need for practice adjustments in case of significant modifications. This study proposes a comprehensive approach to compare different techniques and tests whether their respective dose calculation algorithms give rise to statistically significant differences in the treatment doses for the patient. Methods: Statistical investigation principles are presented in the framework of a clinical example based on 62 fields of radiotherapy for lung cancer. The delivered doses in monitor units were calculated using three different dose calculation methods: the reference method accounts the dose without tissues density corrections using Pencil Beam Convolution (PBC) algorithm, whereas new methods calculate the dose with tissues density correction for 1D and 3D using Modified Batho (MB) method and Equivalent Tissue air ratio (ETAR) method, respectively. The normality of the data and the homogeneity of variance between groups were tested using Shapiro-Wilks and Levene test, respectively, then non-parametric statistical tests were performed. Specifically, the dose means estimated by the different calculation methods were compared using Friedman’s test and Wilcoxon signed-rank test. In addition, the correlation between the doses calculated by the three methods was assessed using Spearman’s rank and Kendall’s rank tests Results: The Friedman’s test showed a significant effect on the calculation method for the delivered dose of lung cancer patients (p 0.001). The density correction methods yielded to lower doses as compared to PBC by on average (−5 ± 4.4 SD) for MB and (−4.7 ± 5 SD) for ETAR. Post-hoc Wilcoxon signed-rank test of paired comparisons indicated that the delivered dose was significantly reduced using density-corrected methods as compared to the reference method. Spearman’s and Kendall’s rank tests indicated a positive correlation between the doses calculated with the different methods. Conclusion: This paper illustrates and justifies the use of statistical tests and graphical representations for dosimetric comparisons in radiotherapy. The statistical analysis shows the significance of dose differences resulting from two or more techniques in radiotherapy.
Faculty
Faculté des sciences et de médecine
Department
Département de Médecine
Language
  • English
Classification
Pathology, clinical medicine
License
License undefined
Identifiers
Persistent URL
https://folia.unifr.ch/unifr/documents/303928
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