Imaging of brain metastases (BMs) has advanced greatly over the past decade. In this review, we discuss the main challenges that BMs pose in clinical practice and describe the role of imaging.Firstly, we describe the increased incidence of BMs of different primary tumours and the rationale for screening. A challenge lies in selecting the right patients for screening: not all cancer patients develop BMs in their disease course.Secondly, we discuss the imaging techniques to detect BMs. A three-dimensional (3D) T1W MRI sequence is the golden standard for BM detection, but additional anatomical (susceptibility weighted imaging, diffusion weighted imaging), functional (perfusion MRI) and metabolic (MR spectroscopy, positron emission tomography) information can help to differentiate BMs from other intracranial aetiologies.Thirdly, we describe the role of imaging before, during and after treatment of BMs. For surgical resection, imaging is used to select surgical patients, but also to assist intraoperatively (neuronavigation, fluorescence-guided surgery, ultrasound). For treatment planning of stereotactic radiosurgery, MRI is combined with CT. For surveillance after both local and systemic therapies, conventional MRI is used. However, advanced imaging is increasingly performed to distinguish true tumour progression from pseudoprogression.FInally, future perspectives are discussed, including radiomics, new biomarkers, new endogenous contrast agents and theranostics.

Background: Melanoma brain metastasis (MBM) is associated with poor outcome, but targeted therapies (TTs) and immune checkpoint inhibitors (ICIs) have revolutionized treatment over the past decade. We assessed the impact of these treatments in a real-world setting. Methods: A single-center cohort study was performed at a large, tertiary referral center for melanoma (Erasmus MC, Rotterdam, the Netherlands). Overall survival (OS) was assessed before and after 2015, after which TTs and ICIs were increasingly prescribed. Results: There were 430 patients with MBM included; 152 pre-2015 and 278 post-2015. Median OS improved from 4.4 to 6.9 months (HR 0.67, p < 0.001) after 2015. TTs and ICIs prior to MBM diagnosis were associated with poorer median OS as compared to no prior systemic treatment (TTs: 2.0 vs. 10.9 and ICIs: 4.2 vs. 7.9 months, p < 0.001). ICIs directly after MBM diagnosis were associated with improved median OS as compared to no direct ICIs (21.5 vs. 4.2 months, p < 0.001). Stereotactic radiotherapy (SRT; HR 0.49, p = 0.013) and ICIs (HR 0.32, p < 0.001) were independently associated with improved OS. Conclusion: After 2015, OS significantly improved for patients with MBM, especially with SRT and ICIs. Demonstrating a large survival benefit, ICIs should be considered first after MBM diagnosis, if clinically feasible.

A data-centric approach prioritizing data quality enabled the development of a generalizable deep learning system that accurately detected and segmented brain metastases of all sizes on MRI scans.

We have read the article “Long-term metabolic evolution of brain metastases with suspected radiation necrosis following stereotactic radiosurgery: longitudinal assessment by F-DOPA PET” by Cicone et al with great interest.¹ Currently, the number of patients with radiation necrosis (RN) after stereotactic radiosurgery (SRS) of brain metastases is increasing, because new treatment strategies have improved the survival of patients with metastatic disease.² To improve long-term monitoring and control of brain metastases after SRS, there is an urgent need for imaging biomarkers to discriminate local progression (LP) from RN during follow-up. Cicone et al address this important issue and report a high diagnostic accuracy of positron emission tomography (PET) using 3,4-dihydroxy-6-[¹⁸F]-fluoro-l-phenylalanine (F-DOPA) to differentiate LP from RN in brain metastases after SRS. However, their data need to be interpreted with caution, since their study has several major limitations. Consequently, this raises the question of which criteria are required for imaging studies reporting on RN and LP in brain metastases.

Background: Immune checkpoint inhibitors (ICIs) are effective treatments for patients with metastatic melanoma, including patients with brain metastasis (BM). However, half of patients with melanoma BM have intracranial progression within 6 months after the start of ICIs. We investigated whether size affects response to ICIs in patients with melanoma BM. Methods: In this single-center cohort study, patients with melanoma BM who were treated with ICIs between 2012 and 2021 were included. Clinical and radiologic features were collected at baseline. Longest axial diameter of all BMs was measured on baseline and follow-up MRI, and segmentation was performed for all BMs on baseline MRI. Lesion-level logistic regression analysis and patient-level survival analysis were performed for early BM progression (ie, within 6 months after start of ICIs) and intracranial progression-free survival (PFS), respectively. Results: A total of 82 patients were included with a total of 464 BMs. At baseline, 37.8% of patients had ≥ 4 BMs and 53.7% of patients had at least one BM with a diameter ≥ 10 mm. In multivariable analysis on the lesion level, baseline BM diameter was associated with early BM progression (odds ratio 1.10, 95%CI 1.05–1.15, P < .001). On the patient level, having at least one BM ≥ 10mm was associated with shorter intracranial PFS (hazard ratio 2.08, 95%CI 1.64–5.56, P < .001). Conclusions: Large BM diameter was associated with a higher risk of early progression after the start of ICIs. Therefore, local therapy should be considered for patients who are treated with ICIs and who have melanoma BMs ≥ 10 mm.

A diagnosis of brain metastasis (BM) significantly affects quality of life in patients with metastatic renal cell cancer (mRCC). Although systemic treatments have shown efficacy in mRCC, active surveillance (AS) is still commonly used in clinical practice. In this single‐center cohort study, we assessed the impact of different initial treatment strategies for metastatic RCC (mRCC) on the development of BM. All consecutive patients diagnosed with mRCC between 2011 and 2022 were included at the Erasmus MC Cancer Institute, the Netherlands, and a subgroup of patients with BM was selected. In total, 381 patients with mRCC (ECM, BM, or both) were identified. Forty‐six patients had BM of whom 39 had metachronous BM (diagnosed ≥1 month after ECM). Twenty‐five (64.1%) of these 39 patients with metachronous BM had received prior systemic treatment for ECM and 14 (35.9%) patients were treatment naive at BM diagnosis. The median BM‐free survival since ECM diagnosis was significantly longer (p = .02) in previously treated patients (29.0 [IQR 12.6–57.0] months) compared to treatment naive patients (6.8 [IQR 1.0–7.0] months). In conclusion, patients with mRCC who received systemic treatment for ECM prior to BM diagnosis had a longer BM‐free survival as compared to treatment naïve patients. These results emphasize the need for careful evaluation of treatment strategies, and especially AS, for patients with mRCC.