Clinical implications of cytogenetic and molecular aberrations in multiple myeloma

Abstract

Multiple myeloma (MM) is an incurable haematological malignancy affecting approximately 7:100,000 people. Monoclonal gammopathy of undetermined significance (MGUS) and ‘smouldering’ MM precede symptomatic MM. Cytogenetics in MM is the most powerful prognostication tool incorporated into different classifications, including the Revised International Staging System (R-ISS) and the Mayo Clinic Risk Stratification for Multiple Myeloma (mSMART). Methods commonly used to test for cytogenetic aberrations include conventional karyotyping and fluorescence in situ hybridisation (FISH), although the difficulty of obtaining metaphases in plasma cells results in low yields. Therefore, new genomic tools are essential to explore the complex landscape of genetic alterations in MM. These include next generation sequencing, a highly sensitive method to monitor minimal residual disease. The serial evolution of MGUS to MM is accompanied by a range of heterogenous genetic abnormalities, divided into primary (involving mostly chromosome 14 translocations and trisomies) and secondary genetic aberration events (involving mostly 17p, 1p, 13q deletions, 1q gain, or MYC translocations). Based on the primary genetic aberration results, strong prognostic features of MM have been identified with distinct clinical characteristics. High risk aberrations include 17p deletion, t(4;14), t(14;16), t(14;20) and chromosome 1 abnormalities. The incorporation of novel drugs and maintenance strategies in conjunction with autologous stem cell transplantation partially overcome the adverse effect of some of these genetic aberrations. Nonetheless, survival remains worse in this group compared to standard risk patients. Clinical decisions regarding treatment should be based on the cytogenetic results. The establishment of individualised and mutation-targeted therapies are of the greatest importance in future studies.