e19560 Background: Despite significant improvements in overall survival over the past 3 decades, MM is still an incurable disease. Most patients will go through multiple lines of therapy and continue treatment for years. With longer time on treatment, there is concern for the development of second primary malignancy (SPM) which is associated with poor outcomes. The present study seeks to characterize the risk of developing SPM for patients with multiple myeloma in a real-world setting. Methods: This retrospective cross-sectional study included adults 18 years and older with multiple myeloma at 21 cancer centers within Kaiser Permanente Northern California between 2011-2023. Demographics, clinical variables, and treatment characteristics were collected for all patients. SPM was defined as any cancer (excluding non-melanoma skin cancer) diagnosed after initial diagnosis of multiple myeloma. Patients were followed for at least 1 year, and SPM was further characterized by type of cancer and time to diagnosis. A Cox proportional hazards model was used to identify demographic and clinical factors associated with the development of SPM. Results: 2,327 patients were diagnosed with multiple myeloma at a median age of 69 years. 42.7% were female.14.5% were Black, 12.0% were Asian/Pacific Islander, 13.5% were Latinx, and 54.8% were White. The majority (57.2%) were never smokers and 15.4% had a cancer diagnosis prior to multiple myeloma diagnosis. 28.2% underwent autologous stem cell transplant (ASCT) and 75.4% received lenalidomide. In total, 8.6% were diagnosed with a SPM. Of those, 24 developed a hematologic malignancy and 181 developed a solid cancer. The median time to diagnosis of SPM from diagnosis of multiple myeloma was 2.4 years. Median overall survival after SPM diagnosis was 1.3 years and only 8 months for those who developed a hematologic malignancy. None of the demographic factors assessed were associated with increased risk of SPMs including age, sex, race, prior cancer history, and smoking history. Notably, lenalidomide use was not associated with increased risk of SPM (HR 0.61; CI 0.24 - 1.58). History of ASCT showed a numerically increased risk of developing a hematologic malignancy, but this was not statistically significant (HR 1.61; CI 0.57 - 4.56). Conclusions: This large, real-world study demonstrates that the development of SPM is a common occurrence for patients with multiple myeloma with poor outcomes. Future studies are needed to better understand how this risk can be mitigated.
Lynch et al. (Thu,) studied this question.
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