Secondary Malignancies in Multiple Myeloma in Korean Patients: A Nationwide Population-Based Study

Purpose This study investigated the incidence of secondary malignancy in multiple myeloma (MM) patients compared with that in the general population using a population-based database covering all residents in Korea. Materials and Methods Based on the national health insurance system in Korea, all people primarily diagnosed with MM between January 1, 2010 to December 31, 2018 were identified. A total of 9,985 MM patients aged >= 20 years in Korea were included. Results Among them, 237 (2.4%) developed secondary malignancies by 2018. The standardized incidence rates (SIRs) of all secondary malignancies in MM patients were 0.87 (95% confidence interval [CI], 0.76 to 0.98), with a higher incidence of hematologic malignancies than in the general population with an SIR of 3.80 (95% CI, 2.61 to 5.00). The incidence rates of both lymphoid malignancy (SIR, 3.56; 95% CI, 2.31 to 4.82) and myeloid malignancy (SIR, 3.78; 95% CI, 1.16 to 6.39) were higher in MM patients than in the general population. In contrast, a lower incidence of solid cancer was observed in MM patients than in the general population (SIR, 0.76, 95% CI, 0.65 to 0.86). There was no significant difference in survival in MM patients without secondary malignancies, with hematologic malignancy, and with solid cancer (p=0.413). Conclusion MM patients had a greater risk of secondary malignancies, especially hematologic malignancies, than the general population. Future studies with a focus on analyzing patients' history, treatment details, and genetic information in various stages of MM patients are needed to better understand the mechanism behind this increased risk.