Morphological MRI features as prognostic indicators in brain metastases

Abstract

Background: Stereotactic radiotherapy is the preferred treatment for managing patients with fewer than five brain metastases (BMs). However, some lesions recur after irradiation. The purpose of this study was to identify patients who are at a higher risk of failure, which can help in adjusting treatments and preventing recurrence.

Methods: In this retrospective multicenter study, we analyzed the predictive significance of a set of interpretable morphological features derived from contrast-enhanced (CE) T1-weighted MR images as imaging biomarkers using Kaplan-Meier analysis. The feature sets studied included the total and necrotic volumes, the surface regularity and the CE rim width. Additionally, we evaluated other nonmorphological variables and performed multivariate Cox analysis.

Results: A total of 183 lesions in 128 patients were included (median age 61 [31-95], 64 men and 64 women) treated with stereotactic radiotherapy (57% single fraction, 43% fractionated radiotherapy). None of the studied variables measured at diagnosis were found to have prognostic value. However, the total and necrotic volumes and the CE rim width measured at the first follow-up after treatment and the change in volume due to irradiation can be used as imaging biomarkers for recurrence. The optimal classification was achieved by combining the changes in tumor volume before and after treatment with the presence or absence of necrosis (p < < 0.001).

Conclusion: This study demonstrated the prognostic significance of interpretable morphological features extracted from routine clinical MR images following irradiation in brain metastases, offering valuable insights for personalized treatment strategies.

Keywords: Biomarkers; Brain metastasis; MRI; Morphological features; Radiation therapy; Response.

Fig. 1

Morphological MRI features described in the study. a-b The contrast-enhanced (CE) volume is shown in blue, with the inner black part representing necrosis and both comprising the total volume of the tumor. Additionally, the CE rim width is depicted in red. c Surface regularity (SR) ranges from 0 to 1, with 1 representing a perfect sphere. Two examples of BMs are presented, with SR values of 0.87 and 0.55

Fig. 2

a Kaplan–Meier plot per-lesion for the surface regularity (SR) in pre-treatment BMs larger than 3 cm³ (n = 77). The p-value corresponds to the log-rank test. b Scatter plot displaying the SR values for BMs before and after treatment (first follow-up, n = 183). The p-value corresponds to the Wilcoxon signed-rank test

Fig. 3

Spearman correlation coefficients between relevant variables of the study. Values larger than 0.7 were regarded as strongly correlated

Fig. 4

Kaplan–Meier plot per lesion for the multivariate analysis combining the ratio of total volume between post and pre-treatment measurements with the presence or absence of necrosis at the first follow up after treatment. The p-value corresponds to the log-rank test. HR – Hazard Ratio