Race-dependent differences in risk, genomics and Epstein-Barr virus exposure in monoclonal gammopathies: Results of SWOG S0120

Abstract

Purpose

Risk of myeloma (MM) is increased in African American (AA) populations compared to European American (EA) cohorts. Current estimates of risk of progression of monoclonal gammopathy of undetermined significance (MGUS) are based largely on studies in EA cohorts. Prospective analyses of this risk in AA cohorts are lacking.

Patients and Methods

Between 2003 and 2011, 331 eligible patients with IgG/A monoclonal gammopathy were enrolled in a prospective observational trial (SWOG S0120).

Results

Of 331 eligible patients, 57 (17%) were of AA descent. The risk of transformation to clinical malignancy in AA patients was significantly lower than in non-AA cohort (2 year risk 5% vs 15%; 5 year risk 13% versus 24%; log rank p=0.047). Differences in risk were evident for both MGUS and AMM. Gene expression profile (GEP) of CD138-purified plasma cells revealed that all molecular MM subsets can be identified in both cohorts. However the proportion of patients with high risk GEP risk score (GEP-70 gene risk > −0.26) was lower in the AA cohort (0% versus 33%, p=0.01). AA cohorts also have higher levels of antibodies against Epstein-Barr nuclear antigen-1 (EBNA-1; p<0.001).

Conclusions

These data provide the first prospective evidence that MM precursor states in AA patients may have lower risk disease compared to non-AA counterparts with lower incidence of high-risk GEP and increased EBV seropositivity. Race-dependent differences in biology and clinical risk of gammopathy may impact optimal management of these patients.

Introduction

Multiple myeloma (MM) is a common hematologic malignancy characterized by growth of clonal plasma cells in the bone marrow and preceded by its precursor stage, monoclonal gammopathy of undetermined significance (MGUS)(1). The underlying cause of MM remains unknown, although recent studies point to a role for chronic antigen stimulation in the pathogenesis of this malignancy(2, 3). Both MM and MGUS are associated with marked racial disparities; incidence of MM is increased in African American (AA) compared to Caucasian/European American (EA) cohorts(4–7). Recent studies suggest some race-dependent differences in genomic changes in MM tumor cells such as a lower proportion of mutations in p53 and greater proportion of t(11:14) in AA cohorts(8–11). Epidemiologic studies suggest that AA cohorts have higher risk and earlier onset of detectable MGUS compared to EA counterparts(12). Here again, the biology and clinical aspects of early stage disease have been mostly studied in EA-enriched cohorts, such as those from Olmstead County in Minnesota(1). Prospective data to evaluate the natural history of monoclonal gammopathies in AA cohorts, particularly from US national cooperative group studies are lacking. Here we describe results of an analysis of the impact of racial background in patients enrolled on SWOG S0120.

Methods

Eligible patients with asymptomatic gammopathies (both MGUS and asymptomatic MM) were enrolled following written and signed informed consent and approval by an institutional review board(13). All studies were conducted in accordance with the Declaration of Helsinki. All patients underwent detailed clinical staging at baseline, followed by uniform follow-up, as described(13). When possible, gene expression profiles of purified CD138+ cells were analyzed as described(13). Resultant GEP data was utilized to determine molecular subtypes and risk score based on a 70-gene model. Antibodies against EBNA-1 and tetanus toxoid were analyzed by enzyme-linked immune assay, as described(14). Baseline features were compared using Chi-square and Fisher’s exact tests, with significance set at p<0.05.

Results

Of 331 eligible patients, 57 (17%) were of AA descent. Patients of AA descent were comparable to non-AA cohorts, with the exception that they were younger and had a higher proportion of females (Table 1). AA cohort also had a lower proportion of patients with reduction in uninvolved immunoglobulins. GEP of purified plasma cells revealed that all of the major molecular subsets of MM are represented in both cohorts (Table 1). However, tumor cells from AA cohort had a lower 70-gene risk score (median score −0.61 versus −0.47, p=0.03) (Table 1, Fig 1a). Overall none of the AA cohort had a GEP-70 risk score >−0.26, previously shown to correlate with risk of progression to clinical MM(13). Patients of AA ancestry had a higher proportion of patients with seropositivity against EBV-derived antigen EBNA-1 compared to non-AA cohorts (89% versus 65%, p<0.001), while the seropositivity against tetanus toxoid as a control antigen was similar in both cohorts (88% versus 87%, p=1) (Table 1). AA cohorts also had higher titer of EBNA-1 reactivity compared to non-AA cohorts (p<0.001)(Fig 1b). In contrast to differences in antibody responses, there were no differences in T cell responses to control viral antigens between AA and non-AA cohorts.

Table 1.

Patient Characteristics by Race

Factor	All Patients	non-AA	AA	P-value
Age >= 65 years	143/331 (43%)	126/274 (46%)	17/57 (30%)	0.028
Female	153/331 (46%)	118/274 (43%)	35/57 (61%)	0.013
MGUS	152/331 (46%)	119/274(43%)	33/57 (57)%)	0.057
SWOG Performance Status 0	228/327 (70%)	191/270 (71%)	37/57 (65%)	0.428
Hemoglobin < 12 g/dL	84/331 (25%)	63/274 (23%)	21/57 (37%)	0.043
Platelets < 240×10^3	206/331 (62%)	175/274 (64%)	31/57 (54%)	0.181
Albumin < 4 g/dL	154/329 (47%)	127/274 (46%)	27/55 (49%)	0.768
Serum B2M > 3 mg/L	86/322 (27%)	72/267 (27%)	14/55 (25%)	0.869
Bone Marrow Plasma Cell >= 10%	176/330 (53%)	152/273 (56%)	24/57 (42%)	0.079
Bone marrow plasma cells >= 20%	84/330 (25%)	74/273 (27%)	10/57 (18%)	0.180
Serum M-protein >= 3 g/dL	34/330 (10%)	32/274 (12%)	2/56 (4%)	0.089
Urine M-protein > 0	48/227 (21%)	43/183 (23%)	5/44 (11%)	0.099
Serum light chain Kappa	190/303 (63%)	157/253 (62%)	33/50 (66%)	0.635
Involved serum FLC > 25 mg/dL	42/228 (18%)	37/197 (19%)	5/31 (16%)	1.000
Inv./uninv. FLC ratio > 10	79/228 (35%)	70/197 (36%)	9/31 (29%)	0.547
Uninvolved immunoglobulins low	212/309 (69%)	184/257 (72%)	28/52 (54%)	0.014
SMM High risk (Mayo 2018)^	42/139 (30%)	38/123 (31%)	4/16 (25%)	0.776
Any Cytogenetic Abnormality	24/250 (10%)	22/216 (10%)	2/34 (6%)	0.753
GEP 70-gene risk > −.26	37/126 (29%)	37/112 (33%)	0/14 (0%)	0.010
GEP CD-1 subgroup	6/126 (5%)	4/112 (4%)	2/14 (14%)	0.133
GEP CD-2 subgroup	28/126 (22%)	27/112 (24%)	1/14 (7%)	0.191
GEP HY subgroup	31/126 (25%)	28/112 (25%)	3/14 (21%)	1.000
GEP LB subgroup	28/126 (22%)	23/112 (21%)	5/14 (36%)	0.303
GEP MF subgroup	17/126 (13%)	16/112 (14%)	1/14 (7%)	0.691
GEP MS subgroup	11/126 (9%)	9/112 (8%)	2/14 (14%)	0.352
GEP PR subgroup	5/126 (4%)	5/112 (4%)	0/14 (0%)	1.000
EBNA-1 antibody positive	212/305 (70%)	162/249 (65%)	50/56 (89%)	<.001
Tetanus antibody positive	266/305 (87%)	217/249 (87%)	49/56 (88%)	1.000
Anti-viral$ T cells present	235/288 (82%)	195/240 (81%)	40/48 (83%)	0.840

n/N (%): n- Number with factor, N- Number with valid data for factor

ND: No valid observations for factor

P-values computed using Fisher’s exact test.

P-values represent a comparison between groups, not against the overall population.

^$Cocktail of viral antigens- EBV, CMV, and influenza

^{^}based on patients with available data

Figure 1.

Immune and genomic variables by race

a. Boxplot of 70-gene risk score (GEP-70) in purified CD138+ tumor cells by race.

b. Boxplot of reactivity to Epstein-Barr nuclear antigen-1 (EBNA-1) by race.

The risk of transformation to clinical myeloma (CMM) requiring initiation of therapy in AA patients was lower than in non-AA cohort (2 year risk 5% vs 15%; 5 year risk 13% versus 24%; log rank p 0.047)(Fig 2a). Outcomes in the entire cohort may in part be due to trends in proportion of MGUS. However, differences in risk were also evident separately for both MGUS (2 year risk 0% versus 2%; 5 year risk 0% versus 9%) and AMM (2 year risk 13% versus 25%; 5 year risk 29% versus 36%)(Fig 2b). Cox regression analysis of factors associated with risk of progression limited to the AA cohort revealed that factors such as bone marrow (BM) plasmacytosis which correlate with increased risk in the non-AA cohort also correlate with an increased risk for transformation to CMM in AA population (Table 2). Interestingly, the presence of reactivity against EBNA-1 was associated with a lower risk of transformation, while the reactivity to tetanus toxoid as a control did not impact the risk of malignancy (Table 2).

Figure 2.

Risk of transformation to clinical MM by race

a. Time to development of clinical MM requiring therapy split by AA (n=57) versus other race (n=274).

b. Time to development of clinical MM requiring therapy based on diagnosis of MGUS or AMM at study entry.

Table 2.

Cox proportional hazard regression analysis in AA and non-AA patients for time to development of clinical MM requiring therapy.

	AA patients			Non-AA patients
Variable	n/N (%)	HR (95% CI)	P-value	n/N (%)	HR (95% CI)	P-value
Age >= 65	17/57 (30%)	2.63 (0.37, 18.71)	0.315	126/274 (46%)	2.06 (1.17, 3.64)	0.011
Female	35/57 (61%)	0.77 (0.11, 5.62)	0.796	118/274 (43%)	0.65 (0.36, 1.17)	0.149
SWOG Performance Status 0	37/57 (65%)	0.51 (0.07, 3.62)	0.492	191/270 (71%)	0.80 (0.43, 1.47)	0.464
Hemoglobin < 12 g/dL	21/57 (37%)	2.59 (0.32, 21.11)	0.360	63/274 (23%)	2.19 (1.23, 3.91)	0.006
Platelets < 240×10^3	31/57 (54%)	7.33E7 (0.00, .)	0.057	175/274 (64%)	1.21 (0.67, 2.17)	0.524
Albumin < 4 g/dL	27/55 (49%)	1.20 (0.17, 8.68)	0.859	127/274 (46%)	2.02 (1.14, 3.56)	0.014
Serum B2M > 3 mg/L	14/55 (25%)	5.95 (0.54, 65.61)	0.098	72/267 (27%)	2.49 (1.42, 4.38)	0.001
Bone marrow plasma cells >= 20%	10/57 (18%)	6.19 (0.85, 45.12)	0.041	74/273 (27%)	4.71 (2.66, 8.35)	<.001
Serum M-protein >= 3 g/dL	2/56 (4%)	0.00 (0.00, .)	0.734	32/274 (12%)	5.49 (3.05, 9.91)	<.001
Urine M-protein > 0	5/44 (11%)	0.00 (0.00, .)	0.610	43/183 (23%)	2.75 (1.36, 5.56)	0.003
Serum light chain Kappa	33/50 (66%)	1.68E7 (0.00, .)	0.177	157/253 (62%)	0.98 (0.55, 1.75)	0.943
Involved serum FLC > 25 mg/dL	5/31 (16%)	4.01E8 (0.00, .)	<.001	37/197 (19%)	3.21 (1.70, 6.08)	<.001
Inv./uninv. FLC ratio > 10	9/31 (29%)	1.33E8 (0.00, .)	0.023	70/197 (36%)	3.21 (1.71, 6.02)	<.001
Uninvolved immunoglobulins low	28/52 (54%)	8.91E7 (0.00, .)	0.039	184/257 (72%)	3.13 (1.33, 7.35)	0.006
EBNA-1 antibody reactivity	N = 56	0.29 (0.09, 0.97)	0.030	N = 249	0.69 (0.51, 0.94)	0.016
Tetanus toxoid antibody reactivity	N = 56	0.92 (0.73, 1.16)	0.461	N = 249	0.98 (0.94, 1.02)	0.266
Antiviral T cells present	40/48 (83%)	1.2E7 (0.00, .)	0.365	195/240 (81%)	0.80 (0.40, 1.62)	0.539

HR- Hazard Ratio, 95% CI-95% Confidence Interval, P-value from Score Chi-Square Test in Cox Regression

All p-values reported regardless of significance.

Discussion

In this paper, we have analyzed data from the first prospective US national cooperative group trial in asymptomatic monoclonal gammopathies to show that precursor states in AA cohorts have lower risk genomic profiles and evidence of altered environmental exposure to EBV. The risk of transformation to clinical malignancy was surprisingly lower in AA cohorts. These data therefore suggest that increased risk of MM observed in AA cohorts is likely not due to higher rate of transformation of MGUS to MM, but likely due to differences in incidence already established at the MGUS stage. These data also support findings from prior studies showing higher prevalence and earlier age of onset of MGUS in AA cohorts(6, 7, 15).

These data also provide early insights into possible mechanisms underlying race-related differences in gammopathy. Several of the clinical features of this cohort such as younger age and relative female predominance are similar to those observed in prior studies(11). Lower GEP-70 risk score in AA cohorts suggests that tumor cells in these patients carry genomic alterations associated with a less aggressive course. Importantly, GEP-70 risk score is particularly driven by genes from chromosome 1q and changes in 1q copy number previously implicated in risk of MGUS progression(13, 16). It is notable that lower incidence of 1q amplification in AA cohorts has also been observed in other large MM datasets(17). Therefore race-related differences in risk may in part be related to differences in genomics and high-risk features such as lower prevalence of 1q21 amplification or p53 mutation(8).

Differences in EBV exposure may be multifactorial. However, AA communities are associated with adverse socioeconomic conditions during childhood, which have been implicated in earlier exposure to EBV by nearly a decade relative to EA counterparts (18). It is notable that EBV is a lymphotropic virus and may lead to chronic alterations in normal B cell homeostasis and immune activation, and in turn impact the timing of onset of gammopathies(18–20). Therefore early EBV exposure may in principle expose AA patients to greater cumulative risk of chronic B-cell dysregulation, which in turn may lead to earlier and greater risk for MGUS(21). Further studies in younger AA adults and even children may be needed to evaluate this question.

An important strength of this analysis is that it is based on a national cooperative group trial with detailed baseline staging and prospective standardized follow up. Potential weaknesses include lack of genetic data on racial admixture(11), and risk of inadvertent selection bias if higher-risk AA patients in communities covered by participating centers somehow had less access to healthcare. As this trial did not have therapeutic intent, this is however the only US cooperative-group study to not exclude lower-risk patients. While this is the largest US cooperative group trial to date in this clinical setting, an important limitation of this analysis is the small number of AA patients. Therefore it would be essential to design prospective observational studies in cooperative group setting with increased participation of AA cohorts to confirm these findings.

In summary, these data support prior studies of MM precursor states showing that AA cohorts are diagnosed at an earlier age and associated with lower tumor burden(7). They also provide preliminary evidence suggesting that these lesions may carry lower genomic risk and are associated with greater EBV exposure. These findings may have important implications for understanding race-related differences in myelomagenesis (2, 3). Racial differences may also impact strategies to prevent MM, which are currently an area of active investigation and include immune modulating drugs, monoclonal antibodies and other combination therapies(22, 23).

Translational Relevance.

These are the first prospectively collected US cooperative group data to compare risk of malignant transformation in African-American cohorts with monoclonal gammopathy. The data show that risk of transformation is surprisingly lower in AA cohorts, which is also supported by lower proportion of high-risk genomic signatures in tumor cells. AA cohorts also have higher EBV exposure, which may contribute to earlier onset of gammopathy.