Advanced radiation therapeutics for the central nervous system

The field of radiation oncology has changed dramatically over the last decade with respect to technical capabilities. We are now able to treat tumors with extreme precision and are at a paradigm shift of changing the fractionation dogma to shorter courses while still treating with radical intent. In addition, the integration of MRI and particle therapy into mainstream radiation oncology has the potential to further our ability to target brain tumors while sparing critical regions of normal brain tissue.

The goal of this supplement is to highlight some of the major changes in radiation therapy as it relates to technology and the central nervous system. More specifically, we provide an up-to-date review of the clinical and technical status as it pertains to the treatment of multiple brain metastases. We have learned from multiple randomized trials that the old standard, whole-brain radiation, is detrimental to a patient’s neuro-cognition and quality of life. Stereotactic radiosurgery is now the dominant treatment for patients presenting with up to 4 metastases. However, current stereotactic radiosurgical technology has overcome the limitations of the past as to the number of lesions treatable. Now, 5, 10, 20 or even more metastases can be focally radiated with excellent local control, both initially and at the time of local or distant brain recurrence. Likewise, larger tumors that were previously under-dosed with single-fraction stereotactic radiosurgery are now treated effectively and safely with high-dose focal hypofractionated stereotactic radiation over the course of a week or so. The rationale and experience with hypofractionated stereotactic radiation is a focus within this supplement.

The next paradigm in radiation oncology is emerging because of two dominant technical directions. First, although the use of protons has been a form of therapy for central nervous system tumors for decades, the technology has only recently evolved to allow for modulation of the proton beam. As a result, the technical paradigm of intensity-modulated proton therapy is at the forefront of radiation oncology and will be reviewed in-depth in this supplement specifically as it applies to the central nervous system. Secondly, MRI has been in place for central nervous system tumors for decades as a stand-alone imaging modality that allows for excellent structural information. But the evolution of MRI to allow for biologic information, as a non-invasive method to understand tumor heterogeneity, is only now at the forefront of integration with radiation delivery. With the recent merging of linear accelerator technology with MRI, the ability to image daily and even during radiation delivery brings about a completely new and potentially powerful shift in radiation oncology, especially for the central nervous system. The state-of-the-art of MRI and radiation oncology specific to brain tumors is summarized in this supplement.

We hope this supplement informs our readers as to the bright future of radiation oncology for our patients and the commitment to improving outcomes with respect to tumor control while simultaneously reducing adverse effects through advances in the technology itself.

Author notes