Retrospective Study Of Incidence Of Thromboses In Chinese Versus African Americans With Multiple Myeloma

Risk of arterial (ATE) and venous thromboembolic events (VTE) is increased in multiple myeloma (MM). Immunomodulator therapy (Imid) concurrent with steroids further increases this risk. Retrospective single arm studies suggest that Asian patients with MM may have a lower risk of TE than in other ethnicities. We performed a retrospective study comparing Chinese (C) and African American (AA) patients in two centers, the Department of Clinical Oncology, Prince of Wales Hospital, the Chinese University of Hong Kong (PWH) and the University hospitals, Case Medical Center, Cleveland, Ohio (CMC), for ethnic differences in incidence of TE in MM.

120 Chinese patients from PWH and 100 AA patients from CMC fulfilling IMWG consensus criteria for MM diagnosis between Jan 1^st 2000 and Dec 31^st 2011 were identified and selected for analysis. Data regarding demographics, comorbidities, myeloma characteristics, therapy and thrombotic complications were collected by electronic and paper chart review. Data collection was censored as of Dec 31^st 2012.

The Chinese cohort comprised more men, lower baseline incidence of diabetes (DM), hypertension (HTN) and non-myeloma related renal failure (CRF), advanced myeloma at diagnosis and more IgA subtype than AA. Over 90% of patients of both groups received chemotherapy. 72% of Chinese and 80% of AA received Imid based treatment. Lenalidomide with steroids was used more often in AA (36.8% AA vs 3.6%C, p<0.0001), Chinese received more thalidomide with steroids. (62.2% C vs 42.1%, p:0.004) Use of thromboprophylaxis (TP) is not routine in PWH, less Chinese were on TP during the disease course (11.7% vs 68%, p<0.0001) or during Imid based treatment. (16% vs 85%, p: 0.0001) Relative rates of aspirin, low molecular weight heparin and warfarin usage for TP were similar across both groups.

Despite lower TP rates, a significantly lower rate of symptomatic VTE was observed in the Chinese. (3.3% vs 22%, p:0.001) The difference in VTE detection persisted on correction for number of imaging studies performed, 24 imaging tests in Chinese and 145 in AA. (16.7% vs 48.3%, p:0.004). Amongst the Chinese, all 4 events (100%) occurred on thalidomide dexamethasone (TD), 3 events (75%) in the absence of TP. In the AA, 21 of 26 events (81%) occurred on Imid based treatment. 12 events (46%) occurred in the absence of TP. On binary logistic regression using race, gender, prior venous thrombosis, any TP, TD and lenalidomide dexamethasone therapy as covariates, AA race (OR: 5.022, 95% CI:1.3- 19.4) and TD therapy (OR: 4.07, 1.26- 3.13) emerged as significant risk factors for VTE. Overall incidence of VTE on TD treatment was 4.5% in Chinese versus 22% in AA. (p:0.002)

An increased number of arterial events were seen in the Chinese (9.2% vs 3% in AA) but the difference did not reach statistical significance. Of the 11 arterial events in Chinese, 5 (46%) occurred on Imid based therapy, 9 events (82%) were in the absence of TP. 7 were cardiac and 4 cerebrovascular. Of the 3 arterial events in AA, 1 (33.3%) occurred on Imids and all patients were receiving TP. 1 was cardiac, 1 abdominal and 1 upper limb.

Our study suggests that the Chinese have a lower risk of VTE than AA in the setting of MM. However , despite lower prevalence of most vascular risk factors in Chinese, ATE rates in Chinese were higher than AA, while not statistically significant. Larger studies are necessary to further elucidate these differences in thrombosis risk and to develop specific guidelines for TP in Asian patients with MM

No relevant conflicts of interest to declare.