Is a contrast-enhanced Magnetic Resonance Imaging (MRI) of the brain necessary to rule out metastases?

From the Guidelines

For brain MRI to detect metastases, contrast is strongly recommended. MRI with contrast (typically gadolinium-based) significantly improves detection of metastatic lesions in the brain compared to non-contrast studies, as highlighted in the most recent guidelines 1. The contrast agent highlights areas where the blood-brain barrier is disrupted, which commonly occurs with metastatic disease. Metastases typically enhance with contrast, making them more visible against normal brain tissue.

Key Considerations

• The use of contrast agents with greater relativity, higher contrast doses, and delays between injection and image acquisition can enhance the detection of metastases 1.
• T1-weighted postcontrast imaging with thin sections/volumetric imaging is recommended for detecting small metastases 1.
• Brain metastases commonly appear as well-demarcated, contrast-enhancing lesions at the subcortical gray–white junction, with peritumoral vasogenic edema commonly present 1.

Exceptions and Alternatives

• The only exceptions to using contrast would be cases where it is contraindicated, such as in patients with severe renal impairment (GFR < 30 mL/min), pregnancy, or known allergic reactions to gadolinium-based contrast agents.
• In these situations, alternative imaging approaches might be considered, but they may be less sensitive for detecting metastatic disease.

Imaging Protocols

• Cranial MRI with pre- and post-contrast T1-weighted, T2-weighted and/or T2-fluid-attenuated inversion recovery (FLAIR) and diffusion-weighted imaging (DWI) sequences is the recommended diagnostic work-up for patients with suspected brain metastases 1.
• The sensitivity of MRI for the detection of brain metastases depends on the technique employed, with influencing factors being field strength, contrast agent type and dose, delay between contrast agent administration and data acquisition, and in- and through-plane resolution 1.

From the FDA Drug Label

In another multicenter study of 49 evaluable adult patients with known intracranial tumor with high suspicion of having cerebral metastases, two doses of gadoteridol were administered. First Gadoteridol Injection 0.1 mmol/kg was injected followed 30 minutes later with 0.2 mmol/kg. In comparison to the 0.1 mmol/kg dose alone, the addition of the 0. 2 mmol/kg dose improved visualization in 67% and improved border definition in 56% of patients. In comparison to non-contrast MRI, the number of lesions after 0.1 mmol/kg increased in 34% of patients. After gadoteridol 0. 2 mmol/kg, this increased to 44%.

The use of contrast (gadoteridol) is recommended for MRI of the brain to rule out metastases, as it improves visualization and border definition of lesions. The administration of a higher dose (0.2 mmol/kg) after an initial dose (0.1 mmol/kg) further enhances the detection of lesions, with an increase in the number of lesions detected in 44% of patients 2.

From the Research

MRI of Brain for Metastases: Contrast or No

• The use of contrast agents in MRI for brain metastases is a topic of discussion, with concerns regarding gadolinium-based contrast agents (GBCAs) and their potential risks 3, 4, 5, 6, 7.
• GBCAs are commonly used for enhancement in MR imaging, but their use has been linked to nephrogenic systemic fibrosis (NSF) in patients with severe renal diseases 4, 6, 7.
• Studies have shown that GBCAs can deposit in the brain, particularly in ferritin-rich areas, but no adverse neurological manifestations have been detected in relation to gadolinium retention 5, 7.
• Alternative contrast agents, such as ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles, have been proposed as a viable option for patients at risk for NSF 3.
• Clinical practice guidelines recommend careful consideration of GBCA administration in patients with kidney disease, with alternative imaging modalities used whenever possible 6.
• The safety of GBCAs has been extensively studied, with updates to the American College of Radiology (ACR) NSF GBCA safety classifications and approaches for strengthening the evidence needed for regulatory decisions 7.

Key Considerations

• Patients with mild-to-moderate chronic kidney disease (CKD) can receive standard doses of GBCA with no additional precautions 6.
• Patients with acute kidney injury, severe CKD, or on dialysis require individual consideration and alternative imaging modalities whenever possible 6.
• Newer GBCAs may be administered with patient consent, citing an exceedingly low risk of developing NSF 6.
• Macrocyclic and newer linear GBCAs are considered lower risk than older linear GBCAs 6, 7.