A low percentage of metastases in deep brain and temporal lobe structures

Abstract

Background. Whole-brain radiotherapy (WBRT) in patients with brain metastases (BM) is associated with neurocognitive decline. Given its crucial role in learning and memory, efforts to mitigate this toxicity have mostly focused on sparing radiation to the hippocampus. We hypothesized that BM are not evenly distributed across the brain and that several additional areas may be avoided in WBRT based on a low risk of developing BM. Methods. We contoured 2757 lesions in a large, single-institution database of patients with newly diagnosed BM. BM centroids were mapped onto a standard brain atlas of 55 anatomic subunits and the observed percentage of BM was compared with what would be expected based on that region's volume. A region of interest (ROI) analysis was performed in a validation cohort of patients from 2 independent institutions using equivalence and onesample hypothesis tests. Results. The brainstem and bilateral thalami, hippocampi, parahippocampal gyri, amygdala, and temporal poles had a cumulative risk of harboring a BM centroid of 4.83% in the initial cohort. This ROI was tested in 157 patients from the validation cohort and was found to have a 4.1% risk of developing BM, which was statistically equivalent between the 2 groups (P < 1 × 10-6 , upper bound). Conclusion. Several critical brain structures are at a low risk of developing BM. A risk-adapted approach to WBRT is worthy of further investigation and may mitigate the toxicities of conventional radiation.

Distribution of brain metastases: low-risk metastasis areas may be avoided when treating with whole-brain radiotherapy

“…We found that the proportion of observed BMs in lowrisk ROIs was only 3.0%, significantly lower than the proportion of expected BMs. Yanagihara et al [18] also found that the brainstem, bilateral thalamus, hippocampus, parahippocampal gyrus, amygdala, and temporal pole showed BM involvement at a rate of 4.83%, and these low-risk ROIs may be avoided when treating with WBRT. However, Yanagihara et al did not report the proportion of patients with BMs in their low-risk ROIs.…”

“…The main purpose of this study was to determine the low-risk and high-risk BM areas through the analysis of [18,20] have reported a difference in the risk of metastasis in different sub-structures of the brain; however, these studies divided the brain into several ROIs, thus, making it difficult to apply this approach in clinical practice. In this study, the whole brain was divided into 11 structures: the frontal lobe, parietal lobe, occipital lobe, temporal lobe, insula, internal structures and the diencephalon, brainstem, cerebellar hemispheres, vermis, corpus callosum, and pituitary.…”

“…Recently, Yanagihara et al [18] conducted a study on 157 patients with BM. Fifty-five patients with anatomically defined ROIs were analyzed.…”

Exploration of spatial distribution of brain metastasis from small cell lung cancer and identification of metastatic risk level of brain regions: a multicenter, retrospective study

“…Quattrocchi et al [ 11 ] have highlighted the non-uniform spatial distribution of BMs in patients with breast and lung cancer patient by using MRI scans. One recent study has demonstrated that several critical brain structures have a low risk of developing BMs, however, only 19 cases (6.9%) of BMs were from SCLC [ 13 ]. Yet, there is still uncertainty about results.…”

The Infratentorial Localization of Brain Metastases May Correlate with Specific Clinical Characteristics and Portend Worse Outcomes Based on Voxel-Wise Mapping

“…The voxel-wise analysis additionally found the differences of BMs volume according to various brain areas and primaries, while also implying the heterogeneity of BMs. Compared to the preferred distribution of infratentorial regions, the hippocampus was demonstrated to have a low risk of developing BMs [ 10 , 36 ]. There was a remarkably low proportion of hippocampus BMs in Figure 3 .…”