Association of reproductive risk factors and breast cancer molecular subtypes: a systematic review and meta-analysis.

BACKGROUND: Associations between reproductive factors and breast cancer (BC) risk vary by molecular subtype (i.e., luminal A, luminal B, HER2, and triple negative/basal-like [TNBC]). In this systematic review and meta-analysis, we summarized the associations between reproductive factors and BC subtypes. METHODS: Studies from 2000 to 2021 were included if BC subtype was examined in relation to one of 11 reproductive risk factors: age at menarche, age at menopause, age at first birth, menopausal status, parity, breastfeeding, oral contraceptive (OC) use, hormone replacement therapy (HRT), pregnancy, years since last birth and abortion. For each reproductive risk factor, BC subtype, and study design (case-control/cohort or case-case), random-effects models were used to estimate pooled relative risks and 95% confidence intervals. RESULTS: A total of 75 studies met the inclusion criteria for systematic review. Among the case-control/cohort studies, later age at menarche and breastfeeding were consistently associated with decreased risk of BC across all subtypes, while later age at menopause, later age of first childbirth, and nulliparity/low parity were associated with increased risk of luminal A, luminal B, and HER2 subtypes. In the case-only analysis, compared to luminal A, postmenopausal status increased the risk of HER2 and TNBC. Associations were less consistent across subtypes for OC and HRT use. CONCLUSION: Identifying common risk factors across BC subtypes can enhance the tailoring of prevention strategies, and risk stratification models can benefit from subtype specificity. Adding breastfeeding status to current BC risk prediction models can enhance predictive ability, given the consistency of the associations across subtypes.

Missed Opportunities for Human Immunodeficiency Virus (HIV) Testing During Injection Drug Use-Related Healthcare Encounters Among a Cohort of Persons Who Inject Drugs With HIV Diagnosed During an Outbreak-Cincinnati/Northern Kentucky, 2017-2018.

BACKGROUND: Persons who inject drugs (PWID) have frequent healthcare encounters related to their injection drug use (IDU) but are often not tested for human immunodeficiency virus (HIV). We sought to quantify missed opportunities for HIV testing during an HIV outbreak among PWID. METHODS: PWID with HIV diagnosed in 5 Cincinnati/Northern Kentucky counties during January 2017-September 2018 who had ≥1 encounter 12 months prior to HIV diagnosis in 1 of 2 Cincinnati/Northern Kentucky area healthcare systems were included in the analysis. HIV testing and encounter data were abstracted from electronic health records. A missed opportunity for HIV testing was defined as an encounter for an IDU-related condition where an HIV test was not performed and had not been performed in the prior 12 months. RESULTS: Among 109 PWID with HIV diagnosed who had ≥1 healthcare encounter, 75 (68.8%) had ≥1 IDU-related encounters in the 12 months before HIV diagnosis. These 75 PWID had 169 IDU-related encounters of which 86 (50.9%) were missed opportunities for HIV testing and occurred among 46 (42.2%) PWID. Most IDU-related encounters occurred in the emergency department (118/169; 69.8%). Using multivariable generalized estimating equations, HIV testing was more likely in inpatient compared with emergency department encounters (adjusted relative risk [RR], 2.72; 95% confidence interval [CI], 1.70-4.33) and at the healthcare system receiving funding for emergency department HIV testing (adjusted RR, 1.76; 95% CI, 1.10-2.82). CONCLUSIONS: PWID have frequent IDU-related encounters in emergency departments. Enhanced HIV screening of PWID in these settings can facilitate earlier diagnosis and improve outbreak response.