In an adult with known metastatic cancer and a new persistent headache for three weeks, should the initial imaging be a contrast‑enhanced CT head?

CT Head With or Without Contrast in Metastatic Cancer Patient with 3-Week Headache

In an adult with known metastatic cancer presenting with a persistent headache for three weeks, you should obtain a contrast-enhanced CT head if MRI is unavailable or contraindicated, but MRI brain with IV gadolinium contrast is the preferred imaging modality and should be pursued whenever possible. 1, 2

Primary Imaging Recommendation

MRI brain with IV gadolinium contrast is the gold standard for evaluating suspected brain metastases in cancer patients with new or persistent headache. 1, 2, 3 The superiority of MRI is substantial:

• MRI detects brain metastases in 24% of cases versus only 10% with CT, representing a more than two-fold increase in detection 1
• Brain metastases characteristically appear as contrast-enhancing lesions at the gray-white matter junction, which are often iso- or hypointense without contrast, making them difficult or impossible to distinguish from normal brain parenchyma on non-contrast imaging 1, 2
• The European Society for Medical Oncology and Society for Neuro-Oncology both establish contrast-enhanced MRI as mandatory for optimal evaluation 2, 1

If CT Must Be Used: Contrast is Essential

If MRI is contraindicated or unavailable, CT head WITH IV contrast is required—non-contrast CT is inadequate for detecting brain metastases. 1, 2

The evidence strongly supports this position:

• The National Comprehensive Cancer Network states that when CT is used, contrast enhancement is essential for adequate evaluation of brain metastases 1
• Contrast enhancement exploits the breakdown of the blood-brain barrier that occurs with metastatic lesions, which is critical for detection 1
• The American College of Radiology notes that gadolinium-enhanced brain MRI is more sensitive than contrast-enhanced CT brain, which in turn is far superior to non-contrast CT 1
• Non-contrast CT should only be used emergently to exclude acute hemorrhage, herniation, or mass effect, and must be immediately followed by contrast-enhanced CT or preferably MRI with gadolinium for definitive evaluation 1

Clinical Context Supporting Urgent Imaging

Your patient's presentation warrants immediate imaging evaluation:

• Headache duration of 3 weeks (≤10 weeks) is an independent predictor of intracranial metastases with an odds ratio of 11.0 4
• In cancer patients with new or changed headache, intracranial metastases occur in 32.4% of cases 4
• The natural history of untreated cerebral metastases is dismal, with median survival less than 2 months 5
• Brain metastases are detected in 10-15% of asymptomatic patients with certain cancers at initial diagnosis, and your patient is symptomatic 2

Red Flags to Assess

While obtaining imaging, evaluate for these high-risk features that increase the likelihood of brain metastases:

• Emesis (odds ratio 10.2 for brain metastases) 6
• Bilateral frontal-temporal headache with pulsating quality and moderate-to-severe intensity (odds ratio 11.9) 6
• Gait instability (odds ratio 7.4) 6
• Extensor plantar response (odds ratio 12.1) 6
• Pain not of tension-type (odds ratio 6.7) 4

Practical Algorithm

1. First-line: Order MRI brain without and with IV gadolinium contrast using standardized Brain Tumor Imaging Protocol 2, 7

   • Required sequences: pre- and post-contrast T1-weighted, T2-weighted/FLAIR, diffusion-weighted imaging, and T2* or susceptibility-weighted sequences 2

2. If MRI contraindicated/unavailable: Order CT head WITH IV contrast 1

   • Never order non-contrast CT alone for this indication 1

3. Emergency situations only: Non-contrast CT may be obtained first to exclude acute hemorrhage or herniation, but must be followed immediately by contrast-enhanced imaging 1

Common Pitfalls to Avoid

• Do not order non-contrast CT head as your definitive study—this will miss the majority of brain metastases 1, 2
• Do not delay imaging based on absence of focal neurological deficits—headache alone in a cancer patient warrants brain imaging with low threshold 5
• Do not assume normal neurological examination excludes metastases—no variable from neurological examination added predictive value in one study, and MRI was warranted in all patients 4