The purpose was to study oral contraceptive (OC) use in relation to breast cancer events and endocrine treatment response in a prospective population-based cohort, because it is unclear whether history of OC use impacts on prognosis in breast cancer patients. Between 2002 and 2011, 994 primary breast cancer patients without preoperative treatment were enrolled in Lund, Sweden and followed until December 2012. History of OC use was obtained from preoperative questionnaires. Tumor characteristics, clinical data, and date of death were obtained from pathology reports, patient charts, and population registries. Among the 948 patients with invasive cancer and no metastasis detected on the post-operative screen, 74 % had ever used OCs. Patients were followed for up to nine years (median follow-up 3 years), and 100 breast cancer events were recorded. Ever OC use was not associated with prognosis, irrespective of duration. However, any OC use before age 20 was associated with a threefold increased risk for breast cancer events in patients <50 years but not in patients ≥50 years (P interaction = 0.009). In patients ≥50 years with estrogen receptor positive tumors, previous OC use at any age was associated with a significantly decreased risk of breast cancer events among patients who received aromatase inhibitors compared to patients who never used OCs (adjusted HR 0.37: 95 % CI 0.15-0.87). OC use was not associated with tamoxifen-response. If confirmed, history of OC use may yield valuable prognostic and treatment predictive information in addition to currently used criteria.

Multiple clinical trials investigate statins' effects in breast cancer. The ABCB1 genotype appears to influence statin response and toxicity in the cardiovascular setting. This exploratory study aimed to investigate the interplay between preoperative statin use, ABCB1 genotype, and tumor-specific expression of the statin target 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR) in breast cancer. Preoperative statin use, ABCB1 C3435T genotype, and HMGCR expression in relation to outcome were analyzed in 985 primary breast cancer patients from a population-based prospective cohort in Sweden from 2002 to 2012. Preoperative statin use (n = 80) was not associated with ABCB1 C3435T genotype (n = 576), HMGCR expression (n = 848), or clinical outcomes. ABCB1 C3435T TT-carriers had lower risk of breast cancer events than any C-carriers (adjusted hazard ratio (HRadj) 0.74; 95%CI 0.49, 1.12), but only in non-statin users (Pinteraction = 0.042). Statin users with TT genotype had higher risk of distant metastasis (HRadj 4.37; 95%CI 1.20, 15.91; Pinteraction = 0.009) and shorter overall survival than other patients (HRadj 3.77; 95%CI 1.37, 10.39; Pinteraction = 0.019). In conclusion, there were nominally significant interactions between ABCB1 genotype and preoperative statin use on clinical outcomes, while preoperative statin use was not associated with outcomes. Since this is an exploratory study of the impact of the ABCB1 genotype in relation to statin use and clinical outcomes in the breast cancer setting, the results should be interpreted with caution and warrant replication in an independent cohort, preferably in a randomized setting. Since statin use is common in breast cancer patients, it would be of interest to further elucidate the clinical impact of the ABCB1 genotype in breast cancer.

Whether previous oral contraceptive (OC) use impacts on prognosis women who subsequently develops breast cancer is unclear. The aim was to study history of OC use in relation to breast cancer events in a prospective population-based cohort. Between 2002 and 2011, primary breast cancer patients without preoperative treatment were enrolled in Lund, Sweden and followed until December 2012. Tumor characteristics, clinical data, and date of death were obtained from pathology reports, patient charts, and population registries. History of OC use was obtained from preoperative questionnaires. Among the 948 patients with invasive cancer and no metastasis detected on the postoperative screen, 74% had ever used OCs. Patients were followed for up to nine years and 100 breast cancer events were recorded. Ever OC users had significantly smaller tumors than patients who never used OCs (Ptrend = 0.013). However, there was a significantly higher frequency of grade III tumors in patients with OCs use before age 20 (Ptrend = 0.013), compared to patients with later start or never use. Ever OC use was not associated with prognosis, irrespective of duration. However, any OC use before age 20 was associated with a 3-fold increased risk for breast cancer events in patients younger than 50 years at diagnosis (adjusted HR 3.26: 95% CI 1.06-10.01) adjusted for age, tumor size, axillary lymph node involvement, histological grade, estrogen receptor status, and body mass index, but not in patients 50 years or older at diagnosis (Pinteraction = 0.009). In conclusion, these findings warrant confirmation in an independent cohort. If confirmed, history of OC use may yield prognostic information in addition to currently used criteria. Citation Format: Louise Huzell, Mia Persson, Maria Simonsson, Andrea Markkula, Christian Ingvar, Carsten Rose, Helena C. Jernström. History of oral contraceptive use in breast cancer patients and risk for early breast cancer events. [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 855. doi:10.1158/1538-7445.AM2015-855