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.
Written by:
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.
doi: 10.1016/j.radonc.2014.07.009
PubMed Abstract
PMID: 25108808
UroToday.com Prostate Cancer Section
