Comparative effectiveness of advanced radiotherapy techniques for brain cancers: A systematic review with an emphasis on dosimetric variability

Abstract

Background: Central nervous system (CNS) cancers pose a significant burden on global health. Radiotherapy remains central to treatment, yet optimal techniques for maximizing tumor control remain controversial due to dosimetric variability. Methods: This systematic review evaluates the effectiveness of six advanced radiation techniques in clinical practice. Following PRISMA guidelines, we analyzed 61 studies from the Web of Science, PubMed, and Scopus, covering the period from 2018 to 2024, which reported on tumor coverage, dose conformity, and organ at risk (OAR) sparing.<br /> Results: Our analysis revealed several key findings: (1) Tomotherapy (TOMO) demonstrated optimal dose homogeneity (HI 0.024-0.3) for hippocampal-sparing applications; (2) Volumetric Modulated Arc Therapy (VMAT) provided superior target coverage (CI 1.16-3.0) with greater efficiency (294 MU vs. Intensity-Modulated Radiation Therapy (IMRT 572 MU)); (3) Proton Beam Therapy (PBT) excelled in pediatric cases, reducing hippocampal dose by 91 (4.8 Gy vs. 52.5 Gy); (4) Image-Guided Radiation Therapy (IGRT) enabled significant spinal cord sparing, with a Dmax reduction of 15 compared to non-IGRT, through precise margin matching; (5) CyberKnife (CK) achieved remarkable accuracy for small lesions (<3 cm), maintaining the optic nerve dose below 2.02 Gy, although the treatment time averaged 220 min for larger targets. This review identified significant variability in OAR exposure across modalities (0.02 to 66.8 Gy), particularly for sensitive structures such as the brainstem (2.41 to 55.62 Gy).<br /> Conclusions: While all modalities achieve acceptable tumor control, VMAT and PBT may provide advantages for complex geometries and pediatric cases, respectively. Prospective trials are needed to establish evidence-based guidelines for selection.