Background and purposeThis 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 materialsA 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. ResultsPTV’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. ConclusionsThe improvements in APs could further reduce toxicities observed in SBRT for organ-confined prostate cancer.