ESR Essentials: bone marrow MRI in oncology-practice recommendations by the European Society of Musculoskeletal Radiology.

Involvement of the bone marrow by metastases from solid tumors or multiple myeloma (MM) is a critical challenge in oncologic imaging. Lesion detection and staging, as well as accurate assessment of treatment response, disease recurrence, and complications, are key to optimal patient management. This article provides recommendations for performing and interpreting bone marrow MRI in cancer patients. MRI should be the primary imaging modality for patients suspected of having skeletal bone metastases or MM, and should replace radiography, bone scintigraphy, and CT for these indications. Protocols must be tailored to the clinical context and to each specific cancer. Whole-body MRI (WB-MRI) is preferred for a comprehensive assessment, while axial skeleton MRI (AS-MRI) is a fast and reliable alternative for targeted or follow-up evaluations. We recommend standardized protocols that incorporate anatomical sequences (preferably fast spin echo T2 Dixon) and diffusion-weighted imaging (DWI). Quantitative biomarkers, e.g., apparent diffusion coefficient (ADC) and fat fraction (FF), should be implemented to improve diagnostic accuracy and evaluate treatment response. Radiologists must be familiar with the typical patterns of bone marrow replacement by cancer cells, response assessment principles, and common imaging pitfalls. Every medical imaging facility should offer optimal bone marrow MRI and implement these recommendations using available MRI systems and existing disease-oriented guidelines. This ESR Essentials illustrates when, how, and why to perform bone marrow MRI to improve diagnostic precision and oncologic care across a broad range of indications. KEY POINTS: Prefer MRI of the bone marrow over radiographs, bone scintigraphy, or CT for suspected bone metastases of solid cancers and for myeloma staging. Use MRI for diagnosis of bone involvement, disease staging, assessment of lesion response to treatment, detection of recurrence, and assessment of osseous complications. Tailor MRI protocol to cancer type following existing guidelines, targeting either the axial skeleton or the "whole body," and using a panel of sequences with fat-sensitive, fast spin echo T2 Dixon and diffusion-weighted sequences as the fundamental components.