Plan quality assessment of modern radiosurgery technologies in the treatment of multiple brain metastases.

Stereotactic radiosurgery (SRS) of multiple brain metastases has evolved over the last 40 years allowing centres to treat an increasing number of brain metastases in a single treatment fraction. HyperArcTMplanning optimisation technique is one such development that streamlines the treatment of multiple metastases with a single isocentre. Several studies have investigated the plan quality of HyperArc compared to CyberKnife or Gamma Knife, however there are limited number of studies that include all three modalities. It is the aim of this study to provide an assessment of plan quality between the three SRS platforms across ten patients with multiple brain metastases ranging from three to eight metastases per patient. Strict planning workflows were established to avoid bias towards any particular treatment platform. Plan quality was assessed through dose to organs at risk, Paddick conformity index (PCI), gradient index (GI), global efficiency index (Gη) and dose to normal brain tissue. Results from this study found mean PCI observed across Gamma Knife plans was significantly lower than HyperArc and CyberKnife. HyperArc plans observed significantly shorter beam-on times which were 10 to 20 times faster than CyberKnife and Gamma Knife plans. Gamma Knife and CyberKnife were found to produce plans with significantly superior GI, global efficiency index and the volume of healthy brain receiving greater than 12 Gy (V12Gy) when compared to HyperArc plans. Lesion volume was seen to influence the relative difference in dose metrics between systems. The study revealed that all three treatment modalities produced high quality plans for the SRS treatment of multiple brain metastases, each with respective benefits and limitations.

(Stereotactic) radiosurgery XIX: spinal radiosurgery--two year experience in a UK centre.

INTRODUCTION: Modern radiotherapy image guidance enables the treatment of extracranial targets with the required accuracy for safe delivery of radiosurgical treatments. The first two years' experience of spinal radiosurgery in a UK radiotherapy centre is reported. MATERIALS AND METHODS: Patients with primary or metastatic spinal lesions were treated using the CyberKnife stereotactic radiotherapy system. Xsight Spine (fiducial-free) tumour tracking software was used in all cases. Treatment was delivered using either a single or a three-fraction schedule, between February 2009 and March 2011. RESULTS: Fifty-three spinal lesions were treated, comprising 14 primary lesions in 12 patients, and 39 metastases in 29 patients. The prescription dose ranged from 8 to 30 Gy in 1-3 fractions. Fifty-nine percent of patients experienced no acute side effects from treatment. There were three cases of acute grade 3 back or nerve root pain, all of which responded to a short course of oral corticosteroids. At a median follow-up of 11.1 months, local control and overall survival were 91 and 65%, respectively. Pain improvement was seen in 75% of symptomatic metastases at 6 months post treatment. CONCLUSIONS: Early UK experience confirms that radiosurgery is well tolerated with excellent local control rates. Longer-term prospective data are needed to clarify the role of spinal radiosurgery for patients in this country.