EPR19-070: Incidence Pattern of Malignant Lymphoma by Cell-Lineage/Cell-Maturity Status in Nagasaki, Japan, 1985–2012: Preliminary Results

Background: Malignant lymphoma (ML) is a heterogeneous neoplasm with a wide range of etiological factors, pathological patterns, incidence rates, and outcomes. Most epidemiological studies have reported the incidence pattern of ML by simply dividing into 2 groups, Hodgkin lymphoma (HL) or non-Hodgkin lymphoma (NHL). However, differences in the incidence pattern by cell-lineage or by cell-maturity have been rarely evaluated. The aim of this study was to characterize the incidence pattern of ML by cell-lineage and cell-maturity in Japanese population. Methods: This is a descriptive study based on regional cancer registry data. We obtained a dataset of anonymized 12,645 cases with ICD-O histology codes of ML diagnosed 1960–2012 from the Nagasaki Prefectural Cancer Registry. From those, we excluded 1,477 records because of codes other than ML, diagnosed before 1985, and possible relapse records of identical cases. Records based on ICD-O-1 or ICD-O-2 were substituted by the corresponding ICD-O-3 code. We also treated patients having multiple types of MLs at same diagnosis date as a single case of “composite/discordant lymphoma,” and patients having multiple types of MLs at different diagnosis date as a single case based on the first lymphoma. We finally confirmed 11,118 patients of ML that occurred in 1985–2012. The overall age-adjusted incidence rate (per 100,000 population) during 1985–2012 was already reported to be 20.5 for men and 12.9 for women. Then we divided them into the following cell-lineage/maturity groups: precursor B (B1), mature B (B2), other B (B3), precursor T (T1), mature T/NK (T2), undetermined cell-lineage NHL (U), HL (H), and other lymphomas (O). Results: The median age at diagnosis of all patients was 69.7 years (interquartile range, 59.4–78.0 years) and male sex were 5,980 (53.8%). The frequency of B-cell lineage, T/NK-cell lineage, and Hodgkin lymphoma were 5,196 (46.7%), 3,257 (29.3%), and 209 (1.9%), respectively, with a significant sex difference (P<.0001). For B-cell maturity, B2 was predominant (84.8%), followed by B3 (14.4%) with a significant sex difference (P<.0001). In T-cell, T2 was predominant (99.4%). Conclusion: This preliminary analysis suggests a significant sex difference in the cell-lineage and cell-maturity of ML. Additional analysis to elucidate whether there are any differences in the incidence pattern by cell-lineage and by cell-maturity of ML between general population and Nagasaki atomic bomb survivors are underway.