Temporal Change in Tumor Volume Following Stereotactic Radiosurgery to a Single Brain Metastasis

Volumetric analysis: Rethinking brain metastases response assessment

Background

The Response Assessment in Neuro-Oncology for Brain Metastases (RANO-BM) criteria are the gold standard for assessing brain metastases (BMs) treatment response. However, they are limited by their reliance on 1D, despite the routine use of high-resolution T1-weighted MRI scans for BMs, which allows for 3D measurements. Our study aimed to investigate whether volumetric measurements could improve the response assessment in patients with BMs.

Methods

We retrospectively evaluated a dataset comprising 783 BMs and analyzed the response of 185 of them from 132 patients who underwent stereotactic radiotherapy between 2007 and 2021 at 5 hospitals. We used T1-weighted MRIs to compute the volume of the lesions. For the volumetric criteria, progressive disease was defined as at least a 30% increase in volume, and partial response was characterized by a 20% volume reduction.

Results

Our study showed that the proposed volumetric criteria outperformed the RANO-BM criteria in several aspects: (1) Evaluating every lesion, while RANO-BM failed to evaluate 9.2% of them. (2) Classifying response effectively in 140 lesions, compared to only 72 lesions classified by RANO-BM. (3) Identifying BM recurrences a median of 3.3 months earlier than RANO-BM criteria.

Conclusions

Our study demonstrates the superiority of volumetric criteria in improving the response assessment of BMs compared to the RANO-BM criteria. Our proposed criteria allow for evaluation of every lesion, regardless of its size or shape, better classification, and enable earlier identification of progressive disease. Volumetric criteria provide a standardized, reliable, and objective tool for assessing treatment response.

Predictors of Survival After Stereotactic Radiosurgery for Untreated Single Non-Small Cell Lung Cancer Brain Metastases: 5- and 10-year Results

BACKGROUND

Stereotactic radiosurgery (SRS) presents as a good treatment option for smaller, deep-seated brain metastases (BMs). This study aims to determine predictors of SRS failure for patients with non-small cell lung cancer BMs.

METHODS

This was a retrospective study of single non-small cell lung cancer BMs treated using SRS. We included patients >18 years with a single, previously untreated lesion. Primary outcome was treatment failure, defined as BMs dimension increase above the initial values. Demographic, clinical, and radiological data were collected to study potential predictors of treatment failure.

RESULTS

Worse rates of progression-free survival (PFS) were associated with heterogeneous contrast enhancement (18.1 ± 4.1 vs. 41.9 ± 4 months; P < 0.001). Better rates of PFS were associated with volumes <1.06 cm3 (log-rank; P = 0.001). Graded prognostic assessment was significantly associated with survival at 120 months (log-rank; P < 0.001). Karnofsky Performance Scale was evaluated in 3 strata: 90-100, 80, and ≤70. Mean survival rates for these strata were 31.8 ± 3.9, 10.6 ± 2.2, and 9.8 ± 2.3 months, respectively (log-rank; P < 0.001). There were no differences regarding presence of extracranial metastases, age, or lesion location. A multivariable logistic regression found that volume <1.06 cm3 was associated with higher survival rates at 10 years (odds ratio: 3.2, 95% confidence interval: 1.3-8.0).

CONCLUSIONS

Contrast-homogeneous metastases and lesions <1.06 cm3 are associated with better rates of PFS. Karnofsky Performance Scale and graded prognostic assessment were associated with more favorable survival rates after 10 years. Volume <1.06 cm3 was the only significant predictor of survival in the multivariable analysis.

MRI Detection of Changes in Tissue Sodium Concentration in Brain Metastases after Stereotactic Radiosurgery: A Feasibility Study

BACKGROUND AND PURPOSE

To date, treatment response to stereotactic radiosurgery (SRS) in brain metastases (BM) can only be determined by MRI evaluation of contrast-enhancing lesions in a long-time follow-up. Sodium MRI has been a subject of immense interest in imaging research as the measure of tissue sodium concentration (TSC) can give valuable quantitative information on cell viability. We aimed to analyze the longitudinal changes of TSC in BM measured with ²³ Na MRI before and after SRS for assessment of early local tumor effects.

METHODS

Seven patients with a total of 12 previously untreated BM underwent SRS with 22 Gy. In addition to a standard MRI protocol including dynamic susceptibility-weighted contrast-enhanced perfusion, a ²³ Na MRI was performed at three time points: (I) 2 days before, (II) 5 days, and (III) 40 days after SRS. Nine BMs were evaluated. The absolute TSC in the BM, the respective peritumoral edemas, and the normal-appearing corresponding contralateral brain area were assessed and the relative TSC were correlated to the changes in BM longest axial diameters.

RESULTS

TSC was elevated in nine BM at baseline before SRS with a mean of 73.4 ± 12.3 mM. A further increase in TSC was observed 5 days after SRS in all the nine BM with a mean of 86.9 ± 13 mM. Eight of nine BM showed a mean 60.6 ± 13.3% decrease in the longest axial diameter 40 days after SRS; at this time point, the TSC also had decreased to a mean 65.1 ± 7.9 mM. In contrast, one of the nine BM had a 13.4% increase in the largest axial diameter at time point III. The TSC of this BM showed a further TSC increase of 80.1 mM 40 days after SRS.

CONCLUSION

Changes in TSC using ²³ Na MRI shows the possible capability to detect radiobiological changes in BM after SRS.