Monoclonal gammopathy of undetermined significance and smoldering multiple myeloma: biological insights and early treatment strategies.

After decades of virtually no progress, multiple myeloma survival has improved significantly in the past 10 years. Indeed, multiple myeloma has perhaps seen more remarkable progress in treatment and patient outcomes than any other cancer during the last decade. Recent data show that multiple myeloma is consistently preceded by a precursor state (monoclonal gammopathy of undetermined significance [MGUS]/smoldering multiple myeloma [SMM]). This observation provides a framework for prospective studies focusing on transformation from precursor disease to multiple myeloma and for the development of treatment strategies targeting "early myeloma." This review discusses current biological insights in MGUS/SMM, provides an update on clinical management, and discusses how the integration of novel biological markers, molecular imaging, and clinical monitoring of MGUS/SMM could facilitate the development of early treatment strategies for high-risk SMM (early myeloma) patients in the future.