Dosimetric and radiobiological comparison of treatment plan between CyberKnife and EDGE in stereotactic body radiotherapy for pancreatic cancer

Li Ma,Ting-ting Cao,Zhi-tao Dai,Man Zhao,Ning Li,Lian Zhu

doi:10.1038/s41598-021-83648-5

Abstract

To perform a comparison of the different stereotactic body radiotherapy (SBRT) plans between the Varian EDGE and CyberKnife (CK) systems for locally advanced unresectable pancreatic cancer. Fifteen patients with pancreatic cancer were selected in this study. The median planning target volume (PTV) was 28.688 cm3 (5.736–49.246 cm3). The SBRT plans for the EDGE and CK were generated in the Eclipse and Multiplan systems respectively with the same contouring and dose constrains for PTV and organs at risk (OARs). Dose distributions in PTV were evaluated in terms of coverage, conformity index (CI), new conformity index (nCI), homogeneity index (HI), and gradient index (GI). OARs, including spinal cord, bowel, stomach, duodenum and kidneys were statistically evaluated by different dose-volume metrics and equivalent uniform dose (EUD). The volume covered by the different isodose lines (ISDL) ranging from 10 to 100% for normal tissue were also analyzed. All SBRT plans for EDGE and CK met the dose constraints for PTV and OARs. For the PTV, the dosimetric metrics in EDGE plans were lower than that in CK, except that D99 and GI were slightly higher. The EDGE plans with lower CI, nCI and HI were superior to generate more conformal and homogeneous dose distribution for PTV. For the normal tissue, the CK plans were better at OARs sparing. The radiobiological indices EUD of spinal cord, duodenum, stomach, and kidneys were lower for CK plans, except that liver were higher. The volumes of normal tissue covered by medium ISDLs (with range of 20–70%) were lower for CK plans while that covered by high and low ISDLs were lower for EDGE plans. This study indicated that both EDGE and CK generated equivalent plan quality, and both systems can be considered as beneficial techniques for SBRT of pancreatic cancer. EDGE plans offered more conformal and homogeneous dose distribution for PTV, while the CK plans could minimize the exposure of OARs.

Highlights

Pancreatic cancer is the fourth leading cause of cancer-related mortality worldwide with a 5-year survival rate approximately 20%1,2
As a new technique born of the synthesis of all of the above-mentioned advances, stereotactic body radiotherapy(SBRT) is becoming more widespread, and it is probably known as a promising method of radiotherapy for pancreatic cancer with greater normal tissue s paring[15,16,17,18]
We made a plan quality comparison in terms of various dosimetric metrics for pancreatic cancer SBRT between Varian CyberKnife and EDGE systems. Both of the two techniques had the capability of producing clinically acceptable plans with adequate planning target volume (PTV) coverage and organs at risk (OARs) sparing. These results showed that EDGE plans offered more conformal and homogeneous dose distribution for PTV, while CK plans had slightly better dose coverage of PTV and the steeper dose fall-off gradient

Summary

Introduction

Pancreatic cancer is the fourth leading cause of cancer-related mortality worldwide with a 5-year survival rate approximately 20%1,2. The general application of EDGE is the intracranial SRS technique, which can eliminate small lesions of intracranial accurately Another application is the SBRT technique of real-time tracking and dynamic irradiation technology, focusing on body dynamic target area constantly[23]. This machine is equipped with flattening filter (FF) and flattening filter free (FFF) beams, and the high resolution multi-leaf collimators (MLC) of 120 leaves with 2.5 mm widths at the isocenter[24,25,26]. It could deliver higher dose rates more effectively and accurately while improving the conformity of dose distribution to the target s imultaneously[25]

Methods

Results

Discussion

Conclusion