Influence of organ at risk definition on rectal dose-volume histograms in patients with prostate cancer undergoing external-beam radiotherapy

摘要: To evaluate rectal dose-volume relations during three-dimensional conformal radiotherapy of patients with prostate cancer by means different volume contours. 55 underwent external-beam radiotherapy. Rectal histograms were calculated for four separately contoured volumes in all resulting groups. In group 1 the outer wall was two CT slices above and below planning target volume. The contour 2 drawn from anal verge up to sigmoid. Furthermore, posterior half rectum both mentioned (groups 1a 2a). Statistical analysis then performed using nonparametric Wilcoxon tests. mean dose 72.9 Gy (standard deviation [SD] ± 2.1 Gy). minimum 70.2 Gy. Mean (± SD) over 50.7 4.6 Gy), 45.2 5.4 43.2 4.2 38.7 5.5 Gy) 1, 2, 1a, 2a, respectively. corresponding receiving ≥ 70 groups 14.0% 5.3%) 11.9% 4.5%). These differences statistically significant. Comparison also revealed a significant difference toward higher doses (p < 0.001). Maximum as well 2a no = 1.0). Data literature on normal-tissue complication probability (rectal bleeding) refer When applying restrictions rectum, contouring becomes factor that determines risk toxicity. results this study show ways significantly influence rectum. organ at should be considered thoroughly patients, especially escalation studies. It is recommended calculate absolute correlate these data toxicity order able achieve comparable among institutions.