Abstract 867: Reproductive factors and risk of B-cell non-Hodgkin lymphoma among women in Los Angeles

Abstract

Abstract Background: Overall, non-Hodgkin lymphoma (NHL) incidence is higher in men than women, and the male to female ratio differs by NHL subtype. Historically, female reproductive characteristics and patterns have been inconsistently linked to NHL risk, though studies on this topic remain limited. Because a woman experiences changes in immune function during pregnancy, that permit her to establish and maintain a successful pregnancy, we hypothesize that such pregnancy-associated changes in immune function could affect the risk of NHL, a cancer of the immune cells. Methods: We conducted a population-based case-control study among women in Los Angeles County comprising 998 histologically confirmed B-cell NHL patients diagnosed 2004-2008 from the Los Angeles Cancer Surveillance Program and 998 individually matched controls (matched on age, race and socioeconomic status). Conditional logistic regression was used to calculate the associations [odds ratios (OR) and 95% confidence intervals (CI)] between female reproductive factors (e.g., ever pregnant; number of full-term pregnancies; breastfeeding) with B-cell NHL overall and unconditional logistic regression was used to calculate the associations with major NHL subtypes. Results: Compared to women who had never been pregnant, women who had full-term pregnancies had 17% decreased risk of B-cell NHL (OR = 0.83, 95% CI = 0.64-1.08); the decreased risk was most pronounced for the diffuse large B-cell lymphoma (DLBCL) subtype (OR = 0.68, 95% CI = 0.47-0.98). Increasing number of full-term pregnancies was inversely associated with B-cell NHL overall (P-trend = 0.02), DLBCL (P-trend = 0.03) and follicular lymphoma (P-trend = 0.04). Women who had reported breastfeeding also had decreased risk of B-cell NHL overall (OR = 0.80, 95% CI = 0.64-1.00) and follicular lymphoma (OR = 0.71, 95% CI = 0.50-1.00). Among women who had full-term pregnancies, women who breastfed for 60 weeks or more had 30% decreased risk of B-cell NHL overall (OR = 0.70, 95% CI = 0.52-0.93; P-trend = 0.06), which was consistent for follicular lymphoma and chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL). Conclusions: Our results provide evidence for an association between female reproductive factors and decreased risk of B-cell NHL, supporting a role for hormonal factors in B-cell NHL etiology. Citation Format: Yani Lu, Jianning Luo, Sophia Wang, Jane Sullivan-Halley, Wendy Cozen, Leslie Bernstein. Reproductive factors and risk of B-cell non-Hodgkin lymphoma among women in Los Angeles. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 867. doi:10.1158/1538-7445.AM2015-867