8038 Background: Studies from the CALGB and IFM have suggested an increased incidence of SPM post ASCT in patients on lenalidomide maintenance. Patients with MM as well as patients post ASCT are inherently at higher risk of SPM. Therefore, assessment of risk factors associated with SPM would be useful in therapeutic decisions re preASCT therapy and post ASCTmaintenance. Methods: We conducted a retrospective cohort study of 841 consecutive MM patients who underwent at least one ASCT at City of Hope from 1989 to 2009. Sixty cases with 70 SPMs were identified. A nested case-control study was also conducted to understand the role of therapeutic exposures associated with SPMs. Controls were MM patients post ASCT matched by year of HCT (±5 years). Results: The median length of follow up was 3.3 yrs. (range 0.3-19.9). Median age at ASCT was 56 yrs (range 18-77). 62% had received a single autologous HCT, 27% tandem autologous HCT, 11% had received multiple HCTs (72 had a second allogeneic HCT)). The overall cumulative incidence of any SPM was 7.4% at 5 years and 15.9% at 10 years; the cumulative incidence of SPMs for patients >55 years approached 21.9% at 10 years. The cumulative incidence of MDS/AML was 1.8% and of solid tumors was 13.0%. Factors examined included age, race, sex, number and individual therapeutic exposures ( pre-ASCT, conditioning, and post-ASCT), disease status at ASCT. Multivariate Cox regression analysis revealed non-Hispanic whites (RR=2.4, 95% CI, 1.2-4.6, p=0.01) and older age (>55) at diagnosis of MM (RR=2.3, 95% CI, 1.3-4.1, p=0.004) to be associated with an increased risk of developing SPMs. Only cumulative thalidomide exposure (both pre-ASCT and post-ASCT) demonstrated a trend toward a positive association (OR=3.5, 95% CI, 0.6-19.4, p=0.15). Six patients (3 cases and 3 controls) were exposed to lenalidomide prior to development of SPM (OR=1.0, 95% CI, 0.14-7.10). Conclusions: This single institution analysis identified non-hispanic whites and older age to be associated with increased risk of developing SPM in pts post ASCT for MM. The trend towards increased risk with thalidomide exposure may be suggestive of a class effect from IMIDs that is not restricted to lenalidomide alone.