Linac-based cone-SRS for intracranial oligometastases: A comprehensive evaluation

Background: This study aimed to determine whether linac-based cone plans offer a more comprehensive advantage over volumetric-modulated arc therapy (VMAT) plans in the stereotactic radiosurgery treatment of up to 5 intracranial oligometastases. Methods: For 59 lesions in 23 patients, noncoplanar multi-arc cone and noncoplanar multi-arc VMAT plans were designed and compared using dosimetry, plan complexity, delivery time, γ-passing rates, and radiobiological indices. Results: The cone plans had significant dosimetric and radiobiological advantages over the VMAT plans, showed no significant benefits in plan complexity and γ-passing rate, and a disadvantage in delivery time. The mean conformity index value for the cone plans was slightly smaller than that for the VMAT plans (0.64 vs 0.68, P > .05), whereas the cone plans had a much better mean gradient index value than that for the VMAT plans (1.79 vs 5.32, P < .001). The mean dose to normal brain tissue was 1.41 Gy for the cone plans and 1.61 Gy for the VMAT plans ( P < .05). V 8 Gy , V 5 Gy , and V 3 Gy were significantly smaller for the cone plans than for the VMAT plans (all P < .05), except for V 12 Gy , which showed no significance. As the number of lesions increased, the advantage of the smaller low-dose volume of the cone plans became more and more evident. Both plans obtained a mean tumor control probability of >99% for planning target volumes ( P > .05), but the mean normal tissue complication probability of normal brain tissue was significantly lower for the cone plans than for the VMAT plans ( P < .05), and both values were much <1%. Conclusion: The linac-based cone-stereotactic radiosurgery plans have more comprehensive advantages and are a better choice for up to 5 intracranial oligometastases.