Whole-body MRI for the evaluation of metastatic lobular breast cancer; current uses and future directions

Abstract Invasive lobular cancer (ILC) metastases are harder to detect radiologically than metastases from invasive breast cancer of no specific type (IBC-NST) due to a unique tumour biology. Metastatic ILC (mILC) spread is also unusual and challenging, favouring sites such as the peritoneum. The sclerotic bone metastases commonly seen with mILC are non-measurable on Computed Tomography (CT) by currently accepted response criteria (RECIST) and are frequently Fluorodeoxyglucose (18F-FDG) PET-CT non-avid. UK/European guidelines recommend CT +/- Bone Scan (BS) or PET-CT for staging and assessment of treatment response in breast cancer however there is increasing evidence that Whole-body MRI (WBMRI) with its anatomical and functional capabilities (offered by diffusion weighted imaging- DWI) can overcome conventional imaging challenges for breast cancer, especially for ILC subtypes. WBMRI is more accurate at identifying additional sites of disease in mILC and the earlier detection of progressive disease (PD) resulting in treatment changes. WBMRI advancements are creating fast, well-tolerated studies and the use of novel Artificial Intelligence (AI) and Machine Learning (ML) techniques may increasingly help with acquisition and reporting speed. There are WBMRI consensus guidelines for several tumour types, but no published guidelines yet exist for breast. It is acknowledged that the published evidence supporting WBMRI is derived mainly from retrospective studies and prospective validation in dedicated cohorts of patients with mILC remains limited. There remains however an unmet need for more effective imaging in this complex patient population and this review article presents the current evidence to support the use of WBMRI in the management of mILC illustrated by cases from clinical practice and discusses the challenges of widespread adoption and potential future applications.