INTRODUCTION: To investigate the dosimetric impact of daily on-line repositioning during a full course of IMRT for prostate cancer.
MATERIALS AND METHODS: Twenty patients were treated with image-guided IMRT. Each pre-treatment plan (Plan A) was compared with a post-treatment plan sum (Plan B) based on couch shifts measured. The delivered dose to the prostate without a daily repositioning was inferred by considering each daily couch shift during the whole course of image-guided IMRT (i.e. plan B). Dose metrics were compared for prostate CTV (P-CTV) and PTV (P-PTV) and for organs at risk. Ten patients were treated with a 5 mm margin and 10 patients with a 10 mm margin.
RESULTS: For plan A vs plan B: the average D95, D98, D50, D mean and EUD were: 76.4 Gy vs 73.9 Gy (p = 0.0007), 75.4 Gy vs 72.3 Gy (p = 0.001), 78.9 Gy vs 78.4 Gy (p = 0.014), 78.7 Gy vs 77.8 Gy (p = 0.003) and 78.1 Gy vs 75.9 Gy (p = 0.002), respectively for P-CTV, and 73.2 Gy vs 69.3 Gy (p = 0.0006), 70.7 Gy vs 66.0 Gy (p = 0.0008), 78.3 Gy vs 77.5 Gy (p = 0.001), 77.8 Gy vs 76.4 Gy (p = 0.0002) and 74.4 Gy vs 69.2 Gy (p = 0.003), respectively for P-PTV. Margin comparison showed no differences in dose metrics between the two plans except for D98 of the rectum in plan B which was significantly higher with a 10 mm margin.
CONCLUSIONS: The absence of daily image-guided IMRT resulted in a significantly less uniform and less homogeneous dose distribution to the prostate. A reduction in PTV margin showed neither a lower target coverage nor a better spare of OAR with and without daily image-guided IMRT.
Written by:
Arnaud A, Maingon P, Gauthier M, Naudy S, Dumas JL, Martin E, Peignaux-Casasnovas K, Truc G, Bonnetain F, Crehange G. Are you the author?
Department of Radiation Oncology, Georges François Leclerc Cancer Center, 21000 Dijon, France; Department of Biostatistics, Georges François Leclerc Cancer Center, 21000 Dijon, France; Department of Radiation Oncology, Division of Medical Physics, Georges François Leclerc Cancer Center, 21000 Dijon, France; Department of Radiation Oncology, Division of Medical Physics, Institut Curie, 75000 Paris, France.
Reference: Phys Med. 2014 Apr 30. pii: S1120-1797(14)00075-1.
doi: 10.1016/j.ejmp.2014.04.006
PubMed Abstract
PMID: 24792687
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