Biological Significance and Prognostic Value of Cytogenetics in 160 Patients with Multiple Myeloma: Predictivity of 13 and/or 14 Monosomies

Until recently, MM was defined using strict clinical pathological criteria that required evidence of specific end-organ damage (CRAB) attributable to the underlying clonal plasma cell disorder. In the case of absence of end-organ damage, patients with clonal plasma cell proliferation were diagnosed either with monoclonal gammopathy of undetermined significance (MGUS) or with smoldering multiple myeloma (SMM). Further, on one hand there have been on-going revisions of the diagnostic criteria for MM and SMM, on the other there have also been revisions of the molecular classification of these disorders; namely, staging and risk. These revisions regarding both the diagnostic criteria and the molecular classification of these disorders are very important because recent advances in understanding these disorders have led to significant progress in the treatment of MM and SMM, in our understanding of disease biology, and in prognostic evaluation for cancer patients. The Revised International Staging System (RISS) combines elements of tumor burden (ISS) and disease biology (presence of high-risk cytogenetic abnormalities or elevated lactate dehydrogenase level) to create a unified prognostic index that helps in clinical care, comparing clinical trial data. The RISS will be of importance in the clinic in terms of counseling patients regarding prognosis, as well as in clinical trials to compare outcomes across clinical trials. The initial cytogenetic classification of SMM also has implications for prognosis as patients with t(4;14) translocation, 17p deletion, and 1q amplification have a higher risk of progression from SMM to MM. Although patients with trisomies are considered to have a better prognosis when diagnosed with MM, they have a higher risk of progression from SMM to MM compared to patients with t(11;14). It is possible that trisomic MM manifests earlier with more obvious bone disease, producing in essence a lead-time bias. Thus, the time from SMM to MM is shortened while the time from MM to death appears longer. There are several molecular subtypes of MM, associated with several unique differences in disease presentation and prognosis. For example, trisomic MM appears to respond particularly well to lenalidomide-based therapy, while t(4;14) MM requires bortezomib-based induction and maintenance for good outcome. In terms of clinical presentation, t(4;14) MM appears to have a lower propensity for bone disease at diagnosis, while t(14;16) MM is often associa