Based on small numbers, recent reports from 3 randomized trials have consistently demonstrated more hematologic malignancies in patients treated with lenalidomide as maintenance (vs placebo). This fact has prompted concern and highlighted the association between multiple myeloma and second malignancies. Furthermore, an excess of acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS) after multiple myeloma has been known for over 4 decades. Most prior studies have been restricted because of small numbers of patients, inadequate follow-up, and limitations of ascertainment of second malignancies. Although the underlying biologic mechanisms of AML/MDS after multiple myeloma are unknown, treatment-related factors are presumed to be responsible. Recently, an excess risk of AML/MDS was found among 5652 patients with IgG/IgA (but not IgM) monoclonal gammopathy of undetermined significance, supporting a role for disease-related factors. Furthermore, there is evidence to suggest that polymorphisms in germline genes may contribute to a person's susceptibility to subsequent cancers, whereas the potential influence of environmental and behavioral factors remains poorly understood. This review discusses current knowledge regarding second malignancies after multiple myeloma and gives future directions for efforts designed to characterize underlying biologic mechanisms, with the goal to maximize survival and minimize the risk for second malignancies for individual patients. (Blood. 2012;119(12): 2731-2737)
IntroductionAfter decades of virtually no progress, multiple myeloma survival has improved significantly in the last 10 years, in younger patients even 2-to 3-fold. 1-3 Indeed, multiple myeloma has seen more remarkable progress in treatment and patient outcomes than any other cancer in the last decade. With improvements in survival, a relatively new clinical challenge that has emerged is the risk of second malignancies. This pattern of increase in second malignancies has been observed in other cancers with available curative therapies and favorable outcomes. Survivors of testicular cancer are at up to 3-fold higher risk of developing a second malignancy than the general population. 4 Survivors of Hodgkin lymphoma have more than 3 times greater risk of solid tumors. Fifteen years after diagnosis, the cumulative mortality from second malignancies exceeds cumulative mortality from Hodgkin lymphoma. 5,6 In the United States alone, the number of cancer survivors has tripled since 1971 and is growing by 2% each year; cancer survivors constitute 3.5% of the United States population. 7 Indeed, secondor higher-order cancers account for 18% of incident cancers in the United States, making them the third most common cancer diagnosis. 7 Based on the National Cancer Institute Surveillance, Epidemiology and End Results (NCI SEER) database, compared with the general population, cancer survivors have a 14% increased risk of developing a malignancy. 7 In the late 1960s, based on a restricted number of patients, an association betwee...