Reproductive factors, oral contraceptive use and breast cancer survival in young women Public Deposited

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  • March 21, 2019
  • Trivers, Katrina F.
    • Affiliation: Gillings School of Global Public Health, Department of Epidemiology
  • While much is known about the effect of clinical factors such as tumor characteristics and molecular markers on breast cancer survival, little is known about the impact of non-clinical factors on survival. Reproductive factors play an important role in the development of breast cancer, and oral contraceptive use is associated with a modest increase in incidence but their impact on survival is unclear. This study examined whether reproductive factors and oral contraceptives were associated with survival among younger breast cancer cases. A population-based cohort of women diagnosed with a first, primary, invasive breast cancer between 1990-1992, aged 20-54 years (n=1264), were followed until January 1, 2000. Detailed information on a variety of characteristics was collected through structured in-person interviews given shortly after diagnosis. Vital status was ascertained through the National Death Index (n=292 deaths). Cox regression methods were used to estimate adjusted hazard ratios (HR) and 95% confidence intervals (CI). Relative to nulliparity, parity of 4 or more births was positively associated with all-cause mortality, [HR (95%CI) = 1.71 (1.09-2.67)]. Increased mortality was observed for having a recent birth prior to diagnosis (?5 vs. >5 years) [1.78 (1.28-2.47)], and was more pronounced among women with a pre-diagnostic body mass index of <25 kg/m2 [2.54 (1.61-4.00)]. Early age at menarche and early age at first birth also modestly increased mortality; history of miscarriage, induced abortion, and ever breastfeeding were not related to survival. Relative to non-recent OC use, recent use of OCs just prior to diagnosis increased all-cause mortality, both for time since first use [<10 years versus 20+ years = 1.77 (0.98-3.21)] and last use [<1 year versus 1+ year = 1.46 (0.91-2.33)]. In particular, the HR was doubled for use of high dose estrogen pills versus low dose use within 5 years of diagnosis [2.38 (1.22-4.62)], or if the most recent pill included the progestin levonorgestrel (versus all other types) [2.00 (1.03-3.87)]. These results implicate the timing of hormonal characteristics in breast cancer progression and may enable a better understanding of how reproductive characteristics and oral contraceptive use influence breast cancer survival.
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  • Gammon, Marilie D.
Degree granting institution
  • University of North Carolina at Chapel Hill
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