Assessing the Bone Metabolic Effect of High-Dose Chemotherapy and Autologous Stem Cell Transplantation in the Lumbar Spine of Multiple Myeloma Patients Using 18F-NaF PET/CT

Introduction: High-dose chemotherapy (HDT) combined with autologous stem cell transplantation (SCT) is an emerging therapy for multiple myeloma, a plasma cell malignancy primarily affecting the bone. While HDT with SCT is known to exacerbate bone resorption, spinous degeneration and osteoporosis, the exact effect and pathophysiology of this therapeutic strategy on lumbar spine degeneration and osteoporosis in MM patients is not fully understood. We employ bone-specific molecular imaging modality, 18F-NaF PET/CT, for its potential to evaluate the effect of HDT with SCT on bone density and metabolism of MM patients.

Methods: The FULIMA clinical trial (NCT02187731) enrolled 70 subjects presumed to have new diagnoses of MM. Among them, a total of 15 eligible patients underwent HDT with SCT therapy and were scanned with 18F-NaF PET/CT pre- and post-treatment. Patients’ trabecular body of the L1-L4 vertebrae was analyzed using semi-automatic algorithm using the delineation program OsiriX on the 18F-NaF PET/CT scans to calculate the mean standardized NaF uptake value and average Hounsfield unit (HU) values.

Results: There was no significant difference in HU values of patients pre- and post-treatment (p= 0.2). On the other hand, NaF uptake of the post-treatment group (average SUVmean= 6.219±1.09) was significantly less than that of the pre-treatment group (average SUVmean= 7.254±1.57), demonstrating 14.27% decrease (p= 0.01).

Conclusion : Although the CT results indicate HDT with SCT has no impact on the bone mineral density in the lumbar spine of MM patients, the PET results suggest that the treatment significantly decrease bone formation in the lumbar spine as measured by NaF uptake and thus may increase the risk for lumbar degeneration and osteoporosis. As such, 18F-NaF PET/CT may be a valuable new imaging modality for the assessment of therapy response in MM patients undergoing HDT with SCT and their risk for spine degeneration and osteoporosis.