Stereotactic radiosurgery versus stereotactic radiotherapy for patients with vestibular schwannoma: a Leksell Gamma Knife Society 2000 debate

By definition, the term "radiosurgery" refers to the delivery of a therapeu tic radiation dose in a single fraction, not simply the use of stereotaxy. Multiple-fraction delivery is better termed "stereotactic radiotherapy." Th ere are compelling radiobiological principles supporting the biological sup eriority of single-fraction radiation for achieving an optimal therapeutic response for the slowly proliferating, late-responding, tissue of a schwann oma. it is axiomatic that complication avoidance requires precise three-dim ensional conformality between treatment and tumor volumes. This degree of c onformality can only be achieved through complex multiisocenter planning. A lternative radiosurgery devices are generally limited to delivering one to four isocenters in a single treatment session. Although they can reproduce dose plans similar in conformality to early gamma knife dose plans by using a similar number of isocenters, they cannot reproduce the conformality of modern gamma knife plans based on magnetic resonance image-targeted localiz ation and five to 30 isocenters. A disturbing trend is developing in which institutions without nongamma kni fe radiosurgery (GKS) centers are championing and/or shifting to hypofracti onated stereotactic radiotherapy for vestibular schwannomas. This trend app ears to be driven by a desire to reduce complication rates to compete with modem GKS results by using complex multiisocenter planning. Aggressive adve rtising and marketing from some of these centers even paradoxically suggest s biological superiority of hypofractionation approaches over single-dose r adiosurgery for vestibular schwannomas. At the same time these centers cont inue to use the term radiosurgery to describe their hypofractionated radiot herapy approach in an apparent effort to benefit from a GKS "halo effect." It must be reemphasized that as neurosurgeons our primary duty is to achiev e permanent tumor control for our patients and not to eliminate complicatio ns at the expense of potential late recurrence. The answer to minimizing co mplications while maintaining maximum tumor control is improved conformalit y of radiosurgery dose planning and not resorting to homeopathic radiosurge ry doses or hypofractionation radiotherapy schemes.