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@ARTICLE{Burchardt:178190,
      author       = {N. A. Burchardt$^*$ and A. H. Eliassen and A. L. Shafrir
                      and B. Rosner and R. Tamimi and R. Kaaks$^*$ and S. S.
                      Tworoger and R. Turzanski-Fortner$^*$},
      title        = {{O}ral contraceptive use by formulation and breast cancer
                      risk by subtype in the {N}urses' {H}ealth {S}tudy {II}: a
                      prospective cohort study.},
      journal      = {American journal of obstetrics and gynecology},
      volume       = {226},
      number       = {6},
      issn         = {0002-9378},
      address      = {St. Louis, Mo.},
      publisher    = {Mosby},
      reportid     = {DKFZ-2021-03188},
      pages        = {821.e1-821.e26},
      year         = {2022},
      note         = {#EA:C020#LA:C020# / 2022 Jun;226(6):821.e1-821.e26},
      abstract     = {Oral contraceptive (OC) use has been associated with higher
                      breast cancer risk; however, evidence on the associations
                      between different OC formulations and breast cancer risk,
                      especially by disease subtype, is limited.To evaluate
                      associations between OC use by formulation and breast cancer
                      risk by disease subtype.This prospective cohort study
                      included 107,069 women from the Nurses' Health Study II with
                      recalled OC use from age 13 to baseline (1989) and updated
                      data on OC use until 2009 collected via biennial
                      questionnaires. A total of 5,799 breast cancer cases were
                      identified through 2017. Multivariable Cox proportional
                      hazards models estimated hazard ratios (HR) and $95\%$
                      confidence intervals $[95\%$ CI] for associations between OC
                      use and breast cancer risk, overall and by estrogen and
                      progesterone receptor and HER2 status. OC use was evaluated
                      by status of use (current, former, and never), duration of
                      and time since last use independently and cross-classified,
                      and formulation (i.e., estrogen and progestin type).Current
                      OC use was associated with higher risk of invasive breast
                      cancer (HR 1.31 $(95\%$ CI 1.09-1.58), vs. never use), with
                      stronger associations with longer duration of current use
                      (>5 years, 1.56 (1.23-1.99); ≤5 years, 1.19 (0.95-1.49)).
                      From >5 years since cessation, risk among former and never
                      users was similar (e.g., >5-10 years since cessation, 0.99
                      (0.88-1.11)). Associations did not differ significantly by
                      tumor subtype. In analyses by formulation, current use of
                      formulations containing levonorgestrel in triphasic (2.83
                      (1.98-4.03)) and extended cycle regimens (3.49 (1.28-9.53)),
                      and norgestrel in monophasic regimen (1.91 (1.19-3.06); vs.
                      never OC users), all combined with ethinyl estradiol, was
                      associated with higher breast cancer risk. No association
                      was observed with current use of the other progestin types
                      evaluated (norethindrone, norethindrone acetate, ethynodiol
                      diacetate, desogestrel, norgestimate, and drospirenone),
                      though sample sizes were relatively small for some of the
                      subgroups, limiting these analyses.Current OC use was
                      associated with higher risk of invasive breast cancer
                      regardless of disease subtype, though risk was comparable to
                      never users 5 years after cessation. In analyses by
                      progestin type, associations were observed for select
                      formulations including levonorgestrel and norgestrel.
                      Assessment of the associations for newer progestin types
                      (desogestrel, norgestimate, drospirenone) was limited by
                      sample size, and further research on more recently
                      introduced progestins is warranted.},
      keywords     = {breast cancer (Other) / epidemiology (Other) / estrogen
                      (Other) / hormonal contraception (Other) / molecular
                      subtypes (Other) / oral contraception (Other) / progestin
                      (Other) / risk factors (Other)},
      cin          = {C020},
      ddc          = {610},
      cid          = {I:(DE-He78)C020-20160331},
      pnm          = {313 - Krebsrisikofaktoren und Prävention (POF4-313)},
      pid          = {G:(DE-HGF)POF4-313},
      typ          = {PUB:(DE-HGF)16},
      pubmed       = {pmid:34921803},
      doi          = {10.1016/j.ajog.2021.12.022},
      url          = {https://inrepo02.dkfz.de/record/178190},
}