Second primary malignancies after autologous hematopoietic cell transplantation for multiple myeloma.

Recent studies demonstrate an increased risk of second primary malignancies (SPMs) in patients with multiple myeloma (MM) receiving maintenance lenalidomide after autologous stem cell transplantation (ASCT). We explored the possibility of other risk factors driving post-ASCT SPMs in patients with MM through analysis of our large transplantation database in conjunction with our Long-Term Follow-Up Program. We conducted a retrospective cohort study of 841 consecutive patients with MM who underwent ASCT at City of Hope between 1989 and 2009, as well as a nested case-control analysis evaluating the role of all therapeutic exposures before, during, and after ASCT. Median duration of follow-up for the entire cohort was 3.4 years (range, 0.3-19.9 years). Sixty cases with a total of 70 SPMs were identified. The overall cumulative incidence of SPMs was 7.4% at 5 years and 15.9% at 10 years when nonmelanoma skin cancers (NMSCs) were included and 5.3% at 5 years and 11.2% at 10 years when NMSCs were excluded. Multivariate analysis of the entire cohort revealed associations of both older age (≥55 years; relative risk, 2.3; P < .004) and race (non-Hispanic white; relative risk, 2.4; P = .01) with an increased risk of SPM. Furthermore, thalidomide exposure demonstrated a trend toward increased risk (odds ratio, 3.5; P = .15); however, an insufficient number of patients were treated with lenalidomide to allow us to accurately assess the risk of this agent. Exclusion of NMSCs retained the association with these variables but was accompanied by loss of statistical significance. This large single-institution analysis identified associations between race and older age and increased risk of developing SPM. The trend toward increased risk with thalidomide exposure suggests a class effect from immunomodulatory drugs that might not be restricted to lenalidomide.