Biological implications of whole-brain radiotherapy versus stereotactic radiosurgery of multiple brain metastases

Abstract

ObjectThe efficacy and safety of treatment with whole-brain radiotherapy (WBRT) or with stereotactic radiosurgery (SRS) for multiple brain metastases (> 10) are topics of ongoing debate. This study presents detailed dosimetric and biological information to investigate the possible clinical outcomes of these 2 modalities.MethodsFive patients with multiple brain metastases (n = 11–23) underwent SRS. Whole-brain radiotherapy plans were retrospectively designed with the same MR image set and the same structure set for each patient, using the standard opposing lateral beams and fractionation (3 Gy × 10).Physical radiation doses and biologically effective doses (BEDs) in WBRT and SRS were calculated for each lesion target and for the normal brain tissues for comparison of the 2 modalities in the context of clinical efficacy and published toxicities.ResultsThe BEDs targeted to the tumor were higher in SRS than in WBRT by factors ranging from 2.4- to 3.0- fold for the mean dose and from 3.2- to 5.3-fold for the maximum dose. In the 5 patients, mean BEDs in SRS (calculated as percentages of BEDs in WBRT) were 1.3%–34.3% for normal brain tissue, 0.7%–31.6% for the brainstem, 0.5%–5.7% for the chiasm, 0.2%–5.7% for optic nerves, and 0.6%–18.1% for the hippocampus.ConclusionsThe dose-volume metrics presented in this study were essential to understanding the safety and efficacy of WBRT and SRS for multiple brain metastases. Whole-brain radiotherapy results in a higher incidence of radiation-related toxicities than SRS. Even in patients with > 10 brain metastases, the normal CNS tissues receive significantly lower doses in SRS. The mean normal brain dose in SRS correlated with the total volume of the lesions rather than with the number of lesions treated.

Evaluation of a dedicated brain metastases treatment planning optimization for radiosurgery: a new treatment paradigm?

“…Analysis of risk factors for brain necrosis showed that V10 and V12 were the most important independent predictors of both symptomatic and asymptomatic radionecrosis indicating that volume is more important than the number of lesions treated [ 17 ]. Furthermore, Xue et al [ 18 ] found that mean normal brain dose correlated with the total volume of the lesions rather than with the treated number of lesions.…”

Operative and peri‐operative considerations in the management of brain metastasis

“…Over the past two decades, the use of WBRT for treatment of up to four BM has fallen out of favor at many centers, calling into question the justification of surgery with literature where WBRT was the sole comparator. [45][46][47][48][49][50][51][52] This shift toward SRS was due to the publication of high-quality data supporting the use of SRS over WBRT, showing comparative efficacy (sometimes even improved survival) and decreased radiation-induced toxicity (eg cognitive decline) associated with SRS ( Figure 4). While the use of SRS as a monotherapy has limitations, which include higher rates of salvage therapy, leptomeningeal disease, and distant tumor recurrences compared to WBRT, 47,53 the overall survival and cost-effectiveness of SRS alone vs SRS + WBRT favored SRS alone in two recent studies for up to 10 metastases.…”

Survival Patterns of 5750 Stereotactic Radiosurgery–Treated Patients with Brain Metastasis as a Function of the Number of Lesions

“…WBRT is generally used as treatment for patients with a high number of BM, while SRS is typically considered for patients with a limited number of BM 16,17 . The threshold for this determination remains an area of active research.…”