Association between peripheral blood cytopenia and cancer mortality: A race‐specific risk factor for cancer death

BACKGROUND: Cytopenia is associated with cancer through mechanisms including clonal hematopoiesis and chronic inflammation. Cytopenia is more prevalent in Black people but its relationship with racial disparities in cancer mortality is unknown. METHODS: Cytopenia was defined in 19,028 Black and White participants recruited between 2003 and 2007 for the REasons for Geographic and Racial Differences in Stroke cohort, based on age‐, sex‐, and race‐adjusted ranges for blood counts. Cancer death was ascertained from Social Security Death and National Death Indexes. Multivariable Cox models estimated the risk of cancer mortality associated with cytopenia, adjusting for demographics (model1), anemia and cancer risk factors (model2), and socioeconomics (model3). Racial differences in the cytopenia‐cancer death association were tested by cross‐product interaction terms. RESULTS: Cytopenia was identified in 383 (2%) participants, 250 (65%) White, and 113 (35%) Black people. With median follow‐up 11.3 years, 1,224 (6.4%) cancer deaths occurred. Cytopenia was associated with increased risk of cancer mortality in model1 (HR = 1.57, 95%CI 1.15–2.24), model2 (HR = 1.67, 95%CI 1.22–2.30), and model3 (HR = 1.59, 95%CI 1.17–2.17). Participants with cytopenia had twofold increased cumulative incidence of cancer death (13% vs. 6.5%, p < 0.01). Race by cytopenia interaction terms showed higher HR for cancer death in Black compared to White participants: 2.01 versus 1.41 (p (interaction) = 0.016, model1), 2.12 versus 1.45 (p (interaction) = 0.009, model2), and 1.82 versus 1.44 (p (interaction) = 0.04, model3). CONCLUSION: In this large, observational biracial prospective study, cytopenia was a risk factor for cancer death, with stronger association in Black than White people. Though race impacted the association of cytopenia with cancer mortality, cytopenia was not a mediator of the racial disparity in cancer mortality.