Whole-Body MR Imaging in Cancer Detection

Whole-body (WB) MR imaging is practical for staging and monitoring cancers such as multiple myeloma, prostate and breast cancers. Increasingly, WB MR imaging is increasingly used to provide reassurance and detect cancers opportunistically. This article details the Oncologically relevant findings Reporting and Data System for consistent image acquisition, interpretation, and reporting. Studies show cancer detection rates of about 1% to 2% in asymptomatic populations. Challenges include high rates of incidental findings; however, multiparametric characterization limits overdiagnosis. Clear communication with participants and physicians, the careful use of interventions, and expert interpretation are vital to minimizing harm.

Key points

•
The Oncologically relevant findings Reporting and Data System (ONCO-RADS) classification system provides a standardized framework for acquiring, interpreting, and reporting whole-body (WB) MR imaging findings, classifying them into 5 categories based on the likelihood of malignancy.
•
For asymptomatic individuals in the general population who are cancer averse, WB MR imaging detects and confirms cancers in approximately 1% to 2% of cases.
•
A significant challenge is the high rate of incidental findings and non-oncologically significant findings, most of which are benign, potentially leading to patient anxiety, unnecessary further investigations, and health system pass-through costs.
•
To minimize harm from overdiagnosis, multiparametric assessments with high specificity criteria, strict adherence to ONCO-RADS guidelines for risk-based management, and clear communication with participants and their clinicians are essential.
•
The American College of Radiology finds insufficient evidence to support WB MR imaging screening for asymptomatic individuals without risk factors or family history, citing concerns about cost and effectiveness.

Abbreviations

CT	computed tomography
DWI	diffusion-weighted imaging
LFS	Li–Fraumeni Syndrome
MCD	multicancer detection
ONCO-RADS	Oncologically relevant findings Reporting and Data System
WB	Whole body

Introduction

Cancer remains a leading cause of global mortality, with a significant proportion of cancer-related deaths stemming from malignancies for which no routine screening methods exist, leading to late-stage diagnoses and poorer outcomes. While established single-cancer screening methods, such as mammography for breast cancer, low-dose computed tomography (CT) for lung cancer, colonoscopy, and cervical smears, have improved survival rates for specific populations, they leave many cancers unscreened. This highlights an unmet need for broader early cancer detection strategies, often referred to as multicancer detection (MCD).

Whole-body (WB) MR imaging has emerged as a promising noninvasive modality for oncologic evaluation, driven by recent technological advances. Unlike conventional imaging techniques, such as PET or CT, WB MR imaging does not involve harmful ionizing radiation, making it particularly beneficial for individuals who require repeat examinations, including children and young adults with genetic cancer predisposition syndromes. It provides a comprehensive, one-step assessment of both the skeleton and soft tissues with high spatial resolution ( Table 1 ). ^,

Table 1

Summary of benefits and challenges of whole-body MR imaging in opportunistic cancer detection

Benefits	Harms/Challenges
Radiation-Free: Does not employ ionizing radiation, making it safer for repeated screenings and vulnerable groups such as children and young adults	Overdiagnosis and overtreatment: High sensitivity can lead to the detection of incidental findings and slow-growing cancers, resulting in unnecessary additional tests, procedures, risks, and out-of-pocket expenses
High Sensitivity for Specific Cancers: Especially good at detecting abnormalities in bone marrow, liver, and soft tissues; helpful in diagnosing multiple myeloma, lymphoma, and sarcoma	Cost and Insurance Coverage: Expensive and often not covered by insurance for general screening; overall cost-effectiveness for population-wide screening remains uncertain
Early Detection Potential: Facilitates the identification of asymptomatic cancers at early stages, thereby increasing the likelihood of successful treatment, especially for cancers with late symptom onset (eg, liver, pancreatic, and renal cancers)	Accessibility and Availability: WB MR imaging is not routinely available at most radiology centers within the United States and is usually performed at specialized care facilities. This restriction can limit overall access and compliance with screening guidelines
Multi-Cancer Detection: Can identify cancers that lack established single-cancer screening tests; research shows a high proportion of non-lung cancers among newly diagnosed cases, emphasizing its usefulness for broad cancer detection	Blind Spots: WB MR imaging does not comprehensively evaluate skin and subcutaneous tissues, gastrointestinal tract, breast, and cervix. WB MR imaging is not a replacement for standard screening methods such as mammography, colonoscopy, or cervical smears. Small cancers may go unnoticed, depending on their location
Comprehensive Assessment: Enables simultaneous evaluation of skeletal and soft-tissue structures, which is essential for cancer detection, staging, follow-up, and assessment of visceral, nodal, and skeletal metastases	Expertise in Interpretation: Accurate interpretation requires highly trained radiologists with knowledge of a wide range of health conditions
Dual Role in Health Screening: It can also detect important non-oncological conditions (eg, vascular abnormalities, metabolic disorders, infections), thereby enhancing its value in proactive and preventive health care	Patient Anxiety: The communication of incidental findings or uncertain results can induce significant anxiety. Such concerns should be proactively managed through clear explanations and the establishment of appropriate follow-up procedures

Whole-Body MR Imaging as a Multicancer Detection Test

The term “screening” traditionally refers to a programmatic, systematic approach to testing a population to identify asymptomatic individuals at risk of a specific disease, often guided by economic considerations to benefit the population. In contrast, “early detection” refers to measures aimed at diagnosing cancers in individuals before the disease becomes incurable (for individual benefit) and is sometimes called “opportunistic” detection ( Fig. 1 ).

A diagram depicts the opportunistic and suspected cancer detection pathways with the progression from healthy cells to metastatic cancer and the roles of screening and multicancer detection. — Fig. 1

The rationale for using WB MR imaging for cancer detection is primarily driven by its inherent rule-out test characteristics. WB MR imaging has high sensitivity for cancer detection. ^, When a high-sensitivity test is applied to a low-disease-prevalence population, this results in a very high negative predictive value, indicating a strong ability to rule out cancer. The rule-out capacity is enhanced by multiparametric MR imaging, which has built-in lesion characterization capability. By cross-correlating imaging features across different MR sequences, WB MR imaging lowers false-positive rates and thereby improves the overall benefit-to-harm ratio.

For cancer-averse individuals seeking reassurance, the peace of mind that comes from a negative WB MR imaging examination is considered the primary benefit, often perceived as outweighing the potential risks and costs associated with incidental finding detection and overdiagnosis. This makes WB MR imaging an attractive option for individuals motivated by cancer worry or a family history of cancer while also enabling the detection of a wide range of cancers, including those not typically covered by standard screening methods.

Whole-body MR imaging protocols for cancer detection

It is essential to distinguish WB MR imaging for general health checks and cancer detection. WB MR imaging is increasingly performed in asymptomatic individuals seeking preventive health assessments focused on overall well-being. The aim is to promote proactive health management and informed lifestyle choices. Imaging examinations aim to identify and manage risk factors for various diseases, including cardiovascular disease (eg, assessment of liver fat for metabolic syndrome risk), obesity (eg, muscle-to-fat ratio or body composition), and to detect potentially serious incidental findings, such as aneurysms.

On the other hand, WB MR imaging for MCD aims to detect cancers promptly, thereby improving outcomes. A standard WB MR imaging cancer detection protocol is often designed to be compliant with the Oncologically relevant findings Reporting and Data System (ONCO-RADS), aiming to standardize acquisition, interpretation, and reporting for cancer screening. Advances in technology and faster protocols have led to greater accessibility and increased applications for WB MR imaging in both oncological and non-oncological settings. ^,

Key Components of a Standard Protocol

Magnetic field strength

Imaging can be performed on either 1.5-T or 3-T MR imaging scanners, provided that good image quality is maintained throughout the entire scan volume. While 3.0-T magnets can improve the signal-to-noise ratio of anatomic sequences, they may also produce more artifacts arising from field inhomogeneity, inconsistent fat suppression, image distortions, and susceptibility effects.

Sequences : The protocol includes both anatomic and diffusion-weighted sequences.

•
Anatomic T1 and T2 weighted and short tau inversion recovery sequences are essential for visualizing anatomic structures and characterizing lesions.
•
T1-weighted acquisitions can be performed using the Dixon technique, which allows for the calculation of relative fat fraction images from fat-only and water-only reconstructions. These can help detect and characterize bone and soft-tissue abnormalities (eg, adrenal lesions, dermoid cysts), as well as incidental findings such as fatty liver infiltration.
•
Diffusion-Weighted Imaging (DWI): DWI is a critical component for assessing tissue cellularity and detecting regions of impeded diffusion, often indicative of malignancy. Images are acquired at multiple b-values, typically including a high b-value (eg, 800–1000 s/mm ²). Advances in MR imaging technology, including deep-learning reconstruction, have improved DWI image quality and reduced acquisition times, making it highly applicable to WB imaging.

The grouping of sequences is tailored to each machine’s capabilities, institutional preferences, imaging planes, required level of detail, and anatomic coverage. Typical sequences can be found in the ONCO-RADS standard.

Anatomic coverage

For opportunistic cancer detection, the protocol typically covers the area from the vertex to the mid-thighs, as distal extremity cancers are rare.

For individuals at higher risk for cancer, including those with cancer predisposition, the standard protocol covers the entire body, from the vertex (top of the head) to the feet, including the proximal upper limbs. Specific examples include:

•
Retinoblastoma (Rb) gene mutation: Field of view from vertex to heels.
•
Constitutional mismatch repair deficiency syndrome: Field of view from vertex to heels (with contrast-enhanced brain MR imaging).
•
Li–Fraumeni syndrome (LFS): Vertex to the heels (contrast-enhanced brain sequences and breast MR imaging are also recommended; often undertaken separately).
•
Succinate dehydrogenase gene mutation: Field of view from skull base to pelvis.

Contrast enhancement

The use of intravenous gadolinium-based contrast agents is generally not recommended in opportunistic cancer detection, primarily due to concerns about gadolinium deposition in the brain and potential for adverse reactions. However, contrast may be considered in higher-risk individuals when necessary to improve diagnostic accuracy or to evaluate additional body parts, such as the brain or breast.

Duration

A protocol aimed at opportunistic cancer detection, which includes whole-spine and multislice axial, T1, T2, and diffusion-weighted imaging covering the vertex to the mid-thighs, can usually be completed within 45 to 50 minutes when accelerated by deep learning based image reconstruction techniques. Additional sequences, such as fluid-attenuated inversion recovery for brain imaging and gradient-echo T1-weighted high-spatial-resolution imaging for lung assessment, can increase examination time.

Protocol Variations and Considerations

WB MR imaging protocols may vary based on factors such as specific clinical questions, patient characteristics, and available resources, including scanner equipment specifications. It is crucial for institutions performing WB MR imaging across a spectrum of indications to implement a core protocol and adds sequences tailored to specific patient needs.

Oncologically relevant findings Reporting and Data System classification and decision support system

The ONCO-RADS is a standardized approach for acquiring, interpreting, and reporting WB MR imaging scans for cancer screening, including those with cancer predisposition syndromes [6]. Developed by an international panel of experts, ONCO-RADS addresses the need for greater consistency in practice. It is based on core elements established in the WB MR imaging metastasis and myeloma standards (MET-RADS and MY-RADS). ^, ONCO-RADS provides standardized imaging and reporting protocols, enhances communication between radiologists and clinicians, supports informed decision-making, and facilitates the delivery of appropriate care by enabling timely interventions and reducing unnecessary tests for benign findings.

Core Aims of Oncologically Relevant Findings Reporting and Data System

The ONCO-RADS system aims to enhance the effectiveness and consistency of WB MR imaging for cancer detection.

1.
Standardized Acquisition: Recommends specific technical parameters for WB MR imaging acquisition to ensure consistent image quality across different centers and scanners.
2.
Structured Interpretation: Provides detailed criteria for interpreting WB MR imaging findings and classifying them based on the likelihood of malignancy, emphasizing a systematic evaluation of multiple anatomic regions.
3.
Standardized Reporting: Promotes structured reporting using a standardized template for clear communication of findings to referring clinicians, including detailed descriptions, anatomic locations, and assigned ONCO-RADS categories.

Oncologically relevant findings Reporting and Data System Categories

The ONCO-RADS 5 category scoring system ( Table 2 ) provides a standardized approach to cataloging WB MR imaging findings. It categorizes lesions into 5 groups based on the likelihood of malignancy, guiding subsequent clinical management. This structured system enhances consistency, facilitates communication between radiologists and clinicians, and supports risk-based decision-making in both opportunistic and high-risk screening settings.

Table 2

Oncologically relevant findings Reporting and Data System categories and clinical implications

Category	Description
ONCO-RADS 1	Normal: No abnormal findings detected
ONCO-RADS 2	Benign finding highly likely: Characteristics strongly suggest a benign process
ONCO-RADS 3	Benign finding likely: Findings are probably benign but may require further evaluation
ONCO-RADS 4	Malignant finding likely: Findings suspicious for malignancy
ONCO-RADS 5	Malignant finding highly likely: Findings strongly suggest malignancy

Risk-Based Management Pathways

The ONCO-RADS system provides risk-based management pathways for abnormal findings, guiding clinicians based on the assigned ONCO-RADS category and the patient’s risk group (general population or higher risk; Figs. 2–4 ):