Ethnic Disparities in Multiple Myeloma: A Comparative Analysis of Hispanic Patients.

Study of ethnic disparities in various malignancies has revealed variation in treatment patterns as well as clinical outcomes. In multiple myeloma (MM) patients, ethnic disparities and clinical variability has been recorded in Caucasian, African-American and Asian populations. Such an analysis has not yet been undertaken for patients with Hispanics decent. Since this is the fastest growing ethnic subgroup in USA, it is increasingly important to investigate the variations in disease that may specifically define this population from MM patients of other ethnic backgrounds. We studied a large cohort of MM patients with Hispanic decent seen at our institution and compared them with the Caucasians (the most predominantly reported MM patient population), to better define biological characteristics and survival in this subgroup.

Patients with plasma cell disorders seen at the University of Southern California were included in the analysis. Demographic, mortality and disease-related clinical characteristics at the time of diagnosis of active MM were evaluated. Chi-square test or Mann-Whitney U test were used where appropriate. A 0.05 nominal significance level was used in all hypothesis testing.

Plasma cell disorders in 160 patients were studied. Among these, 140 had active MM at the time of diagnosis. Patients were divided into Hispanic (H; 54%), Caucasian (C; 21%), African-American (AA; 14%), Asian (A; 6%), and other (O; 5%) subgroups based on race. Median age at diagnosis amongst Hispanic patients was 57 yrs (range 20-85), with 49% males. Advanced stage (>stage 1) disease was observed in 87% and 55% of these patients based on the Durie Salmon (DS) staging system and the International Staging System (ISS), respectively. Renal dysfunction was noted at diagnosis in 9% patients. IgG disease was the most common MM subtype (57%) and kappa light chain involvement was more common than lambda light chain (61% vs. 39%). Presence of bone lesions was noted in 65% of the Hispanic patients, while 8% had non-secretory MM. Median serum M spike at diagnosis was 2.3 gm% (range 0-26.7) and median bone marrow (BM) plasmacytosis at diagnosis was 24.5% (range 1%-100%). Majority of Hispanic patients (89%) never received an autologous stem cell transplant (ASCT) and only 21% ever participated in a clinical trial. Immunomodulatory drugs (IMiDs) were used in 55% and proteasome inhibitors (PI) in 44% of the Hispanic patients over the course of their disease. Median overall survival (OS) amongst Hispanic MM patients was 4.1 yrs (95% CI 3.1, 8.1). Further investigation involved comparison of these characteristics between our Hispanic (n=75) and Caucasian (n=30) patients. Among the demographic parameters, we observed a statistically significant difference between the 2 ethnic groups with respect to median age at diagnosis (H; 57 vs. C; 64, p=0.01). Hispanics had 61% patients <70 yrs of age, while the Caucasians had only 38%. There was no statistically significant difference between the two subgroups with respect to gender, DS stage, ISS stage, M spike at diagnosis, renal dysfunction, MM subtype, presence of lytic lesions at diagnosis, secretor status or clinical trial participation. BM plasmacytosis at the time of diagnosis was significantly lower in the Hispanics (H; 20% vs. C; 40%, p=0.04). The Hispanic population was less likely to undergo ASCT (OR=0.21; 95% CI 0.07, 0.59). There was no significant difference amongst the two ethnic subgroups for median OS (p=0.56), or if OS was compared for type of treatment given; IMiDs (p=0.9) or PI (p=0.3).

Studies of ethnic disparities remain an important area of evaluating management needs of specific patient populations as well as optimal triaging of healthcare resources. There is limited information on biological parameters of disease, clinical management information and survival outcome of Hispanic patients with MM. Here we present disease characteristics and treatment outcomes in this fast growing ethnic subgroup. Although our experience is limited to a single center, it reflects the changing population demographics of USA. We observed important disparities in patient demographics such as young age at diagnosis, as well as variable treatment patterns such as decreased ASCT in Hispanic population. Although several parameters may influence these patterns, our initial indications warrant systematic evaluation in larger patient cohorts. These studies are timely and will help in better understanding of ethnic influences on disease biology and clinical behavior.

No relevant conflicts of interest to declare.