New perspectives offered by nuclear medicine for the imaging and therapy of multiple myeloma

The management of multiple myeloma has fundamentally changed over the years and imaging techniques able to match the therapeutic advances are now much needed. Although many patients now achieve complete response after first-line treatment, relapse is common. Therefore, it would be important to improve the initial prognostic stratification and to detect minimal residual disease after treatment. ¹⁸F-FDG-PET/CT is a useful imaging tool which has a high prognostic value at baseline evaluation and can effectively differentiate active from inactive lesions during induction treatment or after autologous stem-cell transplantation. In combination with biological data, it improves the prediction of relapse. Other PET tracers may soon enter clinical practice and overcome some of the limitations of ¹⁸F-FDG, such as the low sensitivity in detecting early bone marrow infiltration. Excellent results with ¹¹C-Methionine are reported by Lapa and colleagues in this issue of the Journal. ¹¹C-Methionine uptake reflects the increased protein synthesis of malignant plasmocytes and correlates well with bone marrow infiltration. Other promising PET ligands include lipid tracers, such as ¹¹C-Choline or ¹¹C-acetate, and some peptide tracers, such as ⁶⁸Ga-Pentixafor, that targets CXCR4 (chemokine receptor-4), which is often expressed with high density by myeloma cells. Malignant plasma cells are radiosensitive and thus potentially amenable to systemic radionuclide therapy. Indeed, excellent preclinical results were obtained with radioimmunotherapy targeting CD38. Also, preliminary clinical results with peptides targeting CXCR4 (e.g. ¹⁷⁷Lu- or ⁹⁰Y-Pentixather) are encouraging. Multiple myeloma may represent a renewal of the already strong partnership between hematologists and nuclear medicine physicians.