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

• Published in: Radiation oncology (London, England) England), 2014-09, Vol.9 (1), p.205-205, Article 205
• Main Authors: Chaikh, Abdulhamid, Giraud, Jean-Yves, Perrin, Emmanuel, Bresciani, Jean-Pierre, Balosso, Jacques
• Format: Article
• Language: English
• Subjects: Algorithms; Analysis; Comparative analysis; Humans; Mathematics; Medical Physics; Methodology; Methods; Patients; Physicists; Physics; Programming languages; Radiation Oncology - standards; Radiation therapy; Radiometry - standards; Radiotherapy; Radiotherapy Dosage; Radiotherapy Planning, Computer-Assisted - standards; Statistical analysis; Statistical methods; Statistics; Statistics as Topic; Studies; Variance analysis
• ISSN: 1748-717X; 1748-717X
• DOI: 10.1186/1748-717X-9-205

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. 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. The Friedman's test showed a significant effect on the calculation method for the delivered dose of lung cancer patients (p