Multiple myeloma (MM) is a malignancy characterized by clonal expansion of malignant plasma cells in the bone marrow, with a median survival of about 6 years [1], [2]. It is the second most common hematologic malignancies in the United States (US), affecting 32,270 estimated new cases and 12,830 estimated deaths in 2022 [3]. MM is more common in males than females, and is twice as common in Blacks than Whites [1]. MM remains mostly incurable, highlighting a critical need to identify risk factors for appropriate prevention.

Despite extensive epidemiology research in the past two decades, including works from the International Lymphoma Epidemiology Consortium (InterLymph) Myeloma Working Group, risk factors for MM, and racial/ethnic disparities in particular, remain poorly understood [4]. To date, known risk factors for MM include genetic susceptibility, a family history of MM [5], [6], older age [7], monoclonal gammopathy of undetermined significance (MGUS) [8], [9], and obesity [10], [11]. Findings are inconsistent on risk factors such as occupational exposure to ionizing radiation [12], pesticides [13], [14], [15], [16], and occupations such as firefighter, hairdresser and metal processer [17], [18]. Importantly, these risk factors do not fully explain the excess risk of MM in Blacks.

To improve our understanding of potential environmental risk factors for MM, we conducted a geospatial analysis of population-based MM incidence between 2013 and 2017 in the US. We hypothesized that the distribution of MM incidence in the US is not random. Our goal is to identify both global clusters and local outliers of MM incidence that could provide insights on etiologic factors.