Multimodal Imaging-Based Potential Visualization of the Tumor Microenvironment in Bone Metastasis.

Dong-Yeon Kim,Su Woong Yoo,Jang Bae Moon,Ayoung Pyo,Seong Young Kwon,Changho Lee

doi:10.3390/cells10112877

Abstract

Bone metastasis (BM) is the most common malignant bone tumor and a significant cause of morbidity and mortality for patients with cancer. Compared to other metastatic organs, bone has unique characteristics in terms of the tumor microenvironment (TME). Precise assessments of the TME in BM could be an important step for developing an optimized management plan for patient care. Imaging approaches for BM have several advantages, such as biopsy not being required, multiple site evaluation, and serial assessment in the same sites. Owing to the developments of new imaging tracers or imaging modalities, bone TME could be visualized using multimodal imaging techniques. In this review, we describe the BM pathophysiology, diagnostic principles of major imaging modalities, and clinically available imaging modalities to visualize the TME in BM. We also discuss how the interactions between various factors affecting the TME could be visualized using multimodal imaging techniques.

Highlights

Bone is one of the major target sites for metastasis
In the two sections, we introduce multimodal imaging techniques to visualize the tumor microenvironment (TME) in Bone metastasis (BM) according to two factors, namely primary lesion and bone microenvironment
When the primary lesion is located in the thyroid, lung, liver, or kidney, osteoclast activation and its interaction with the bone stroma lead to an osteolytic pattern on computed tomography (CT) [47,48,49,50] and low signal intensity (SI) in T1-weighted images (T1WIs) on magnetic resonance imaging (MRI) [51,52,53,54]. 18F-FDG positron emission tomography (PET)/CT generally depicts high FDG uptake in BM lesions from the lung [45,55,56], whereas those from the liver or kidney show low FDG uptake [57,58], which is related to FDG avidity of the primary lesion to some extent

Summary

Introduction

Bone is one of the major target sites for metastasis. Bone metastasis (BM) is the most common malignant bone tumor and a significant cause of morbidity and mortality for patients with cancer. This radiotracer shows rapid clearance from blood and soft tissues, which results in good image contrast as early as 2 h after injection [36] It accumulates in areas of increased osteoblastic activity and increased blood flow and has an advantage for detecting osteoblastic metastases, in breast or prostate cancers [23]. MRI with dynamic contrast enhancement (DCE) has recently been investigated for the diagnosis of spinal BM, showing the ability to detect vertebral body infiltration and tumor vascularity [43] The latter characteristic could permit MRI with DCE to contribute to evaluation of the response to antiangiogenic therapies [20]. 18F-FDG PET/CT has been reported to detect osteolytic, osteoblastic, and mixed lesions, it showed high sensitivity for detecting lytic metastases compared with bone-seeking radiotracers, such as 99mTc-labeled diphosphonate and 18F-sodium fluoride [13,31]. Its specificity can be low for the differential diagnosis between BM and active inflammatory lesions, such as infectious spondylitis or recent traumatic fracture, as 18F-FDG can be taken up by inflammatory as well as tumor cells

Imaging Patterns Based on Primary Tumor Characteristics

Multimodal Imaging According to the Primary Tumor Site and Histologic Type

Image Findings of Bone Metastasis

Imaging Patterns Based on the Bone Microenvironment

Conclusions