Single isocenter treatment planning techniques for stereotactic radiosurgery of multiple cranial metastases

Highlights • DCA in most cases is superior to VMAT for multi metastases single isocenter SRS. • Normal brain V12Gy was significantly reduced with DCA, predicting for lower S-NEC. • Maximum doses to critical organs-at-risk were significantly lower with DCA. • Conformity was comparable between VMAT and DCA.
Background and purpose Whole brain radiation therapy use has decreased in favor of stereotactic radiosurgery (SRS) for the treatment of multiple brain metastases due to reduced neurotoxicity. Here we compare two single isocenter radiosurgery planning techniques, volumetric modulated arc therapy (VMAT) and dynamic conformal arcs (DCA) in terms of their dosimetric and delivery performance. Materials and methods Sixteen patients with 2– 18 brain metastases (total 103; median 4) previously treated with single fraction SRS were replanned for multiple lesion single isocenter treatments using VMAT and DCA using different treatment planning systems for each and three different plan geometries for DCA. Plans were evaluated using the Paddick conformity index, normal tissue V12Gy, the probability for symptomatic brain necrosis (S-NEC), maximum organ-at-risk (OAR) point doses, and total number of monitor units (MU). Results Conformity was not significantly different between VMAT and DCA plans. VMAT plans showed a trend towards higher MU with a median difference between 18% and 24% (p ≤ 0.09). Median V12Gy differences were 7.0 cm3–8.6 cm3 favoring DCA plans (p