Are Racial Disparities Behind More Secondary Primary Malignancies in MM?
HOUSTON  In the last 10 years, overall survival in symptomatic multiple myeloma has significantly improved because of the use of novel therapies. One result has been an increase in the incidence of second primary malignancies (SPM) in patients with MM, according to research available at the 2021 American Society of Clinical Oncology (ASCO) annual meeting.1  A study team led by the Baylor College of Medicine and including researchers from the Boston and Durham, NC, VA Healthcare Systems explained that more frequent SPMs are related to several factors. The researchers hypothesized, however, that racial disparities might also be contributors. The authors noted that very few studies with large, high-quality datasets have evaluated racial disparities in SPMs in MM. To remedy that, they set out to track patterns of incidence of SPMs in veterans with MM, focusing on inequities. To do that, the team conducted a retrospective cohort study based on electronic health records (EHR) and cancer registry data recorded in the VAs Corporate Data Warehouse (CDW) between Jan. 1, 1999, and Jan. 1, 2018. Age, race, gender, treatment era, smoking status, and stage at MM diagnosis all were taken into consideration. Researchers documented 8,467 veterans, nearly all male, with MM. Based on self-reports, the race of participants was 59.4% white, 25.7% African-American and 14.9% other or unknown. After 7.5 years of follow-up, 430 (5.1%) of the MM patients developed SPM, while 8,037 did not. Of the original group, 982 had received hematopoietic stem cell transplants, and those patients appeared to have a higher rate of developing SPM, 6.62%, compared to those who had not received HSCT, 4.87%. Of the 380 veterans with SPM, most, 88.3%, had solid tumors, and 11.6 % had hematological malignancies. Of those with solid tumor SPM, the largest percentage, 29.7%, were diagnosed with prostate cancer; 16.6% with digestive tract cancers. 14.4% with lung cancer and 12.6% with bladder/renal/testicular cancer. The cumulative incidence of developing SPM increased steadily over time for the duration of this study period of 7.5 years from diagnosis, according to researchers, who noted that the median age of diagnosis for white veterans was 68.2 years but was several years younger, 64.3 years, for African-Americans. The authors calculated the hazard ratio for AA vs. whites to develop SPMs at 1.21 (0.975-1.505) (p = 0.0823). However, the risk of prostate cancer was significantly higher in AA with an adjusted hazard ratio of 1.81 (1.196-2.739) (p = 0.005), they added. No racial disparities were observed in the incidence of other types of SPMs.  One finding was that the risk of SPMs does not plateau over a patients lifetime, according to the study team, which pointed out that HSCT was found to be an independent predictor of SPM, while smoking and Agent Orange were not. Noting that their study includes one of the largest groups of AA with MM in published literature, researchers concluded. AA did not have a higher incidence of SPMs overall; but had a significantly higher incidence of prostate cancer than whites. We hope to develop an individualized predictive model for SPM in patients with MM.