Room: Exhibit Hall
Purpose: Non-isocentric CyberKnife stereotactic radiotherapy techniques for treatment to the prostate have been shown to give good local control and prostate-specific antigen response. This study looks to investigate the viability of using CyberKnife SBRT to treat the prostate and nodes in combination with Cesium-131 implants for selected favorable high-intermediate/high-risk, non-metastatic prostate cancer. This will provide convenience for patients travelling long distances to receive highly conformal hypofractionated radiation with the potential for similar outcomes as a standard external beam boost fractionation.
Methods: An SBRT test plan is generated and optimized in MultiPlan (Version 5.1) software. The planning target volume includes the prostate, seminal vesicles, and lymph nodes and is treated to a dose of 25 Gy in 5 fractions to 95% of the volume. Treatment quality is evaluated based on target coverage, normal tissue sparing, homogeneity and conformality index, and treatment efficiency.
Results: A preliminary result showed adequate coverage and comparable results to standard fractionation external beam delivery. Due to the large volume, the conformality for the prostate and nodal targets individually are higher, but acceptable for the whole PTV with a value of 1.28 at 95% coverage. The homogeneity index was calculated to be 1.37 and the delivery time per fraction is 51 minutes.
Conclusion: CyberKnife-based SBRT for treatment of prostate and nodes to a uniform dose appears to be a practical method of delivery. The conformal dose distribution takes a feasible amount of time to deliver in significantly fewer fractions than LINAC-based VMAT. Additional plans are currently being optimized to decrease delivery time and increase conformality and dose fall-off for normal tissue sparing.