Significance of PET/CT Imaging in Myeloma Assessment: Exploring Novel Applications beyond Osteolytic Lesion Detection and Treatment Response

In multiple myeloma (MM), specific cytokines produced by plasma cells disrupt the equilibrium between osteoblasts and osteoclasts. As a result, MM patients experience an increase in osteoclast activity and a decrease in osteoblast activity. This disparity is fundamental to the development of myeloma bone disease. Lytic lesions, which are a feature of MM, can result in pathologic fractures and excruciating pain. For many years, whole-body X-ray radiography has been the standard imaging method for identifying lytic lesions. However, its sensitivity is limited because it can only detect lesions once the bone mass has been reduced by 30% to 50%. Hence, utilizing advanced and sensitive imaging modalities, such as positron emission tomography (PET) fused with computed tomography (CT), is crucial for the early detection of osteolytic lesions. Among radiotracers used in PET imaging, 1⁸F-fluorodeoxyglucose ([18F]FDG) is the most commonly employed in the field of oncology. Currently, most guidelines include [18F]FDG PET/CT in the assessment of myeloma patients, particularly for detecting osteolytic lesions, evaluating treatment response, and assessing extramedullary and residual disease. Nonetheless, in recent years, new applications of PET/CT for evaluating myeloma have been investigated. These include assessing aspects such as bone turnover, dual-time-point imaging (early and delayed scans), the impact of chemotherapy on the brain (commonly known as ‘chemo brain’), innovative PET radiotracers, and the use of artificial intelligence technology. This article aims to provide a comprehensive review of both conventional and innovative uses of PET/CT in evaluating multiple myeloma.