Oral Contraceptive, Menopausal Hormone Therapy Use and Risk of non-Hodgkin Lymphoma in the California Teachers Study

Abstract

Abstract Objective: To evaluate whether use of oral contraceptives (OCs) or menopausal hormonal therapy (MHT) is associated with B-cell non-Hodgkin lymphoma (NHL). Methods: Within the prospective California Teachers Study cohort, women under age 85 with no history of hematopoietic cancer were followed from 1995 through 2007 for diagnosis of B-cell NHL. Overall, 547 women of 116,779 women eligible for analysis of OC use and 402 of 54,758 postmenopausal women eligible for analysis of MHT use developed B-cell NHL. Relative risks (RR) and 95% confidence intervals (CI) were estimated by fitting multivariable Cox proportional hazards models. Results: Women who used OCs had marginally lower risk of B-cell NHL than women who had never used OCs (RR = 0.86, 95% CI = 0.69-1.06). The reduced risk was most pronounced among women who started OCs before age 25, but did not decrease with increasing duration. No association with MHT was observed when MHT ever users were compared to the never users (RR = 1.05, 95% CI = 0.83-1.33); this result was consistent across formulations of MHT [unopposed estrogen therapy (ET), combined estrogen and progestin therapy (EPT)]. Among women who had never used MHT, women with a bilateral oophorectomy had three times greater risk than those with natural menopause (RR = 3.15, 95% CI = 1.62-6.13), whereas there was no association with bilateral oophorectomy among women who had used MHT. In stratified analyses according to hysterectomy and oophrectomy status, ET and EPT did not affect risk for women with natural menopause or those with hysterectomy who had at least part of an ovary remaining. Among women who had a bilateral oophorectomy, ET reduced risk of NHL (RR = 0.41, 95% CI = 0.21-0.82). Conclusion: These data suggest that ET use decreases the risk of B-cell NHL among women with both ovaries removed, but not among women retaining at least part of an ovary. In other subgroups MHT does not influence risk. Additional study of associations of MHT and OCs with B-cell NHL are warranted.