P-159: Increased risk of second primary malignancy and mortality at ten years after stem cell transplant for Multiple Myeloma: an analysis of 14,532 Patients

Abstract

<h3>Background</h3> The landscape for patients with multiple myeloma has improved dramatically over the last 15 years. Immunomodulatory imide drugs (IMiDs) have shown great efficacy, in both the setting of initial therapy and as maintenance after autologous stem cell transplant (ASCT). Concern has been raised, however, regarding the risk of second primary malignancies (SPMs) that appear to be associated with the use of IMiD agents. SPMs are a known sequela of multiple myeloma treatment, particularly as a consequence of maintenance lenalidomide status-post stem cell transplant (SCT). The benefit of SCT has become less clear with the utilization of newer, more effective initial therapies <h3>Objectives</h3> To determine the effect of SCT on SPM risk and overall survival in multiple myeloma patients at 5 and 10 years after treatment initiation. <h3>Methods</h3> We used TriNetX, a global federated health research network providing access to electronic medical records (diagnoses, procedures, medications, laboratory values, genomic information) from approximately 58 Million patients in 49 large Healthcare Organizations. We created two patient cohorts who had all received treatment with thalidomide, lenalidomide, or pomalidomide. One cohort had received SCT while the other had not. Both cohorts were then analyzed for the development of all non-myeloma malignancies which occurred at least one year after treatment initiation. <h3>Results</h3> At 5 years, SPMs were 5.8% more likely in patients who received stem cell transplant (22.4% vs 16.6%, RR 0.741, p value <0.0001). 5-year survival favored transplanted patients by 2.38% (64.85% vs 62.474%, p value 0.0044) but 10-year survival favored patients who did not receive transplant by 1.44% (42.279% vs 40.838%, p value 0.0279). The Kaplan-Meier curves cross at year 6. <h3>Conclusions</h3> With use of newer treatment regimens, the small 5-year survival benefit derived from stem cell transplant in multiple myeloma patients is completely eliminated in year six by mortality that may be attributed to increased second primary malignancies. Survival in transplanted patients is inferior by year 10. Stem cell transplants in these patients should only be performed in selective cases and guided by life expectancy.