BACKGROUND AND PURPOSE: This study is to determine if the overlap-volume histogram (OVH)-driven planning methodology can be adapted to robotic SBRT (CyberKnife Robotic Radiosurgery System) to further minimize the bladder and rectal doses achieved in plans manually-created by clinical planners.
METHODS AND MATERIALS: A database containing clinically-delivered, robotic SBRT plans (7.25Gy/fraction in 36.25Gy) of 425 patients with localized prostate cancer was used as a cohort to establish an organ's distance-to-dose model. The OVH-driven planning methodology was refined by adding the PTV volume factor to counter the target's dose fall-off effect and incorporated into Multiplan to automate SBRT planning. For validation, automated plans (APs) for 12 new patients were generated, and their achieved dose/volume values were compared to the corresponding manually-created, clinically-delivered plans (CPs). A two-sided, Wilcoxon rank-sum test was used for statistical comparison with a significance level of p< 0.05.
RESULTS: PTV's V(36.25Gy) was comparable: 95.6% in CPs comparing to 95.1% in APs (p=0.2). On average, the refined approach lowered V(18.12Gy) to the bladder and rectum by 8.2% (p< 0.05) and 6.4% (p=0.14). A physician confirmed APs were clinically acceptable.
CONCLUSIONS: The improvements in APs could further reduce toxicities observed in SBRT for organ-confined prostate cancer.
Wu B, Pang D, Lei S, Gatti J, Tong M, McNutt T, Kole T, Dritschilo A, Collins S. Are you the author?
Department of Radiation Medicine, Georgetown University Hospital, Washington, USA; Department of Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins University, Baltimore, USA.
Reference: Radiother Oncol. 2014 Aug 6. pii: S0167-8140(14)00304-1.