Reproductive factors and lymphoid neoplasms in Europe: findings from the EpiLymph case-control study.

BACKGROUND: The study of lymphomagenesis has rarely focused on hormonal factors. Higher incidence rates are observed for many lymphoma subtypes in men compared with women suggesting an underlying association. Our goal was to investigate the association between reproductive factors and lymphomas. METHODS: The Epilymph study is a multicenter case-control study carried out in six European countries from 1998 to 2004. Female cases of mature T-cell neoplasms (n = 52), Hodgkin lymphoma (n = 147), and mature B-cell neoplasms (n = 795), including its common subtypes, and their respective controls (n = 1,141) frequency matched by age, gender, and center were considered. RESULTS: An odds reduction of 29% (95% CI -46 to -6%) was observed for mature T-cell neoplasms for each child increase among parous women and of 13% (95% CI -19 to -7%) for mature B-cell neoplasms; while no association was observed for Hodgkin lymphoma. By B-cell neoplasm subtypes, these associations were found for chronic lymphocytic leukemia/small lymphocytic lymphoma (-21%, 95% CI -31 to -9%) and diffuse large B-cell lymphoma (DLBCL; -14%; 95% CI -23 to -3%). Overall, no associations were observed with age at first and last pregnancy, and ever use of hormonal contraceptives and lymphoma. Higher odds ratios for a short-term use of hormonal contraceptives (<5 years), but not for a long-term use, were observed for mature B-cell neoplasms, DLBCL, and follicular lymphoma compared with never use. CONCLUSION: These data support the hypothesis that increased parity confers a protective effect against lymphoma. Less clearly, our results also indicate that hormonal contraceptives could play a role.