MRI for response assessment in metastatic bone disease.

BACKGROUND: Beyond lesion detection and characterisation, and disease staging, the quantification of the tumour load and assessment of response to treatment are daily expectations in oncology.

METHODS: Bone lesions have been considered "non-measurable" for years as opposed to lesions involving soft tissues and "solid" organs like the lungs or liver, for which response evaluation criteria are used in every day practice. This is due to the lack of sensitivity, specificity and measurement capabilities of imaging techniques available for bone assessment, i.e. skeletal scintigraphy (SS), radiographs and computed tomography (CT).

RESULTS: This paper reviews the possibilities and limitations of these techniques and highlights the possibilities of positron emission tomography (PET), but mainly concentrates on magnetic resonance imaging (MRI).

CONCLUSION: Practical morphological and quantitative approaches are proposed to evaluate the treatment response of bone marrow lesions using "anatomical" MRI. Recent developments of MRI, i.e. dynamic contrast-enhanced (DCE) imaging and diffusion-weighted imaging (DWI), are also covered.

KEY POINTS: • MRI offers improved evaluation of skeletal metastases and their response to treatment. • This new indication for MRI has wide potential impact on radiological practice. • MRI helps meet the expectations of the oncological community. • We emphasise the practical aspects, with didactic cases and illustrations.