2University of Texas, MD Anderson Radiation Oncology Outreach Center at American Hospital, İstanbul, Turkey
3Yıldız Technical University Faculty of Medicine, Department of Bioengineering, İstanbul, Turkey
4University of Texas, MD Anderson Cancer Center, Department of Radiation Oncology, Houston, USA
Abstract
Objective: In order to seek a lower toxicity risk prediction in patients with prostate cancer, we have evaluated whether prescribing a potential
hybrid radiotherapy of intensity-modulated radiotherapy (IMRT) & volumetric modulated arc therapy (VMAT) optimization might increase
sparing of organs at risk (OAR) and target dose conformity.
Methods: The cohort for this dosimetric planning study included ten consecutive prostate cancer patients previously treated with double arc
VMAT to 78 Gy. New optimized hybrid arc plans for a combination of IMRT (8 step-and-shoot fix fields: 225°, 260°, 295°, 330°, 30°, 65°, 90°,
135°) and VMAT (182°-178° clockwise) besides new IMRT (8 step-and-shoot fix fields: 225°, 260°, 295°, 330°, 30°, 65°, 90°, 135°) plans were
generated per patient. Dose volume histogram parameters were compared between treated VMAT, new IMRT and new optimized hybrid arc
plans for OAR doses.
Results: The optimized hybrid arc technique revealed significantly lower rectum (p=0.005) and bladder (p= 0.005) doses compared to stand
alone VMAT and IMRT.
Conclusion: The optimized hybrid arc technique appears to combine the advantages of IMRT and VMAT to provide a more conformal and
homogeneous plan with better OAR sparing in comparison to standalone VMAT or IMRT plans.