Recent studies have reported an increased risk of second primary malignancies (SPM) following multiple myeloma (MM) diagnosis associated with novel anti-myeloma treatments. We evaluated the risk of SPM among 36 491 MM cases reported to the Surveillance, Epidemiology, and End Results program (SEER) between 1973 and 2008. We calculated overall and site-specific standardized incidence ratio (SIR) and 95% confidence intervals (CI) for 2012 SPM cases diagnosed within the 35-year follow-up. There was no significant overall risk of SPM (SIR=0.98; 95% CI=0.94-1.02); however, there were multiple site-specific risk patterns. The risk of breast and prostate cancer was significantly decreased overall and across age, latency and the year of diagnosis strata. There was an ∼50% increased risk of colorectal cancer 5 years after MM diagnosis (Ptrend<0.001). The risk of hematological malignancies was significantly increased, notably for acute myeloid leukemia (AML; SIR=6.51; 95% CI=5.42-7.83). There was a significant decreasing trend for AML over time, particularly for patients ≥65. However, no significant change in risk was noted after the introduction of autologous stem cell transplant among younger patients (<65 years). On the basis of observed trends for overall SPM as well as AML, no association between the introduction of novel therapies and SPM following MM has emerged in this large population-based study.
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