Stereotactic radiosurgery for intracranial metastases: linac-based and gamma-dedicated unit approach

For intracranial metastases, the role of stereotactic radiosurgery (SRS) or fractionated stereotactic radiotherapy is well recognized. Historically, the first technology, for stereotactic device able to irradiate a brain tumor volume, was Gamma Knife(®) (GK). Due to the technological advancement of linear accelerator (Linac), there was a continuous increasing interest in SRS Linac-based applications. In those decades, it was assumed a superiority of GK compared to SRS Linac-based for brain tumor in terms of dose conformity and rapid fall-off dose close to the target. Recently, due to the Linac technologic advancement, the choice of SRS GK-based is not necessarily so exclusive. The current review discussed in details the technical and clinical aspects comparing the two approaches for brain metastases.