Lymphoid malignancies in U.S. Asians: incidence rate differences by birthplace and acculturation.

BACKGROUND Malignancies of the lymphoid cells, including non-Hodgkin lymphomas (NHL), HL, and multiple myeloma, occur at much lower rates in Asians than other racial/ethnic groups in the United States. It remains unclear whether these deficits are explained by genetic or environmental factors. To better understand environmental contributions, we examined incidence patterns of lymphoid malignancies among populations characterized by ethnicity, birthplace, and residential neighborhood socioeconomic status (SES) and ethnic enclave status. METHODS We obtained data about all Asian patients diagnosed with lymphoid malignancies between 1988 and 2004 from the California Cancer Registry and neighborhood characteristics from U.S. Census data. RESULTS Although incidence rates of most lymphoid malignancies were lower among Asian than white populations, only follicular lymphoma (FL), chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL), and nodular sclerosis (NS) HL rates were statistically significantly lower among foreign-born than U.S.-born Asians with incidence rate ratios ranging from 0.34 to 0.87. Rates of CLL/SLL and NS HL were also lower among Asian women living in ethnic enclaves or lower SES neighborhoods than those living elsewhere. CONCLUSIONS These observations support strong roles of environmental factors in the causation of FL, CLL/SLL, and NS HL. IMPACT Studying specific lymphoid malignancies in U.S. Asians may provide valuable insight toward understanding their environmental causes.