MRI in melanoma surveillance
Brain MRI; whole-body MRI; gadolinium-enhanced MRI
MRI is the imaging of choice in melanoma for two distinct purposes — CNS surveillance (small intracranial metastases missed by CT and PET-CT) and soft-tissue characterisation of locoregional, in-transit and bone/marrow disease. UK practice uses contrast-enhanced brain MRI as part of routine surveillance from stage IIB upwards per NG14 §1.9.15, and dedicated regional MRI to characterise palpable masses, suspected in-transit metastases and post-treatment change. Whole-body MRI is an emerging modality with selected indications including paediatric melanoma surveillance and patients with relative contraindications to PET-CT.
Brain MRI — CNS surveillance
- Recommended for surveillance of resected stage IIB / IIC / III melanoma and during active treatment of advanced disease.
- NG14 §1.9.15 schedule for resected stage III — brain MRI as part of CE-CT brain protocol; many UK centres use dedicated MRI brain (1.5T or 3T) with contrast.
- Detects small (< 5 mm) metastases that PET-CT and CT miss.
- Particular value at the first signs of neurological symptoms — headache, focal deficit, seizure, cognitive change.
- BRAF-mutant disease has higher CNS metastasis propensity — lower threshold for imaging.
Soft-tissue MRI
- Dedicated regional MRI for:
- Suspected in-transit metastases — characterisation, depth, vascular relationship, surgical planning.
- Locoregional recurrence at the primary site — depth, fascial involvement, perineural spread.
- Palpable nodal disease — pre-operative planning for lymphadenectomy.
- Bone or joint involvement.
- STIR / fat-saturated T2 sequences plus T1 pre and post gadolinium.
- Diffusion-weighted imaging adds value in differentiating tumour from inflammation.
Whole-body MRI
- Emerging modality combining anatomic and functional imaging with no ionising radiation.
- Particular value in paediatric melanoma surveillance and patients with multiple primaries.
- Sensitivity for visceral metastases approaching PET-CT in some studies, but availability and reporting expertise are limiting factors in the UK.
- Useful adjunct for patients with relative contraindications to iodinated contrast or radiation concerns.
Practical points
- Gadolinium-based contrast — caution in renal impairment (NSF risk with linear agents; current macrocyclic agents have negligible risk).
- Claustrophobia and metal implants — pre-screen.
- Protocol the request — clinical history (stage, treatment, suspected location) directs sequence selection.
- Read MRI alongside any prior CT and PET-CT at MDT.
References
- NICE NG14. Melanoma: assessment and management. London: NICE; 2015 (last updated 27 July 2022), recommendations 1.7 and 1.9.15.
- Schubert T et al. Whole-body MRI in oncology — current applications. Eur J Radiol; 2020.
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