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April 5, 2026Cancer Research

Abstract 2343: Reproductive factors associated with breast cancer risk by subtypes: Findings from the Southern Community Cohort Study.

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Why the study?

Reproductive factors may influence breast cancer etiology through hormonal pathways that differ by molecular subtypes, but their subtype-specific associations needed investigation.

Do reproductive factors influence the risk of specific breast cancer subtypes in women?

Population

42,922 women aged 40-79 years (69.2% Black)

Comparison

Reproductive factors and their association with breast cancer risk across molecular subtypes

Design

Prospective cohort study

Follow-up

Up to 213 months

Key result

Multiparity (≥3 births) reduced the risk of luminal A-like (HR 0.74) and B-like (HR 0.53) breast cancers, but increased the risk of ER-/PR- disease (HR 1.71).

Authors

RGRishabh GuptaWWWanqing WenWZWei Zheng

Discussion

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Member takes

Overview

Should not yet change practice; extends evidence of etiologic heterogeneity in breast cancer subtypes.

Key Points

  • The research aims to explore the relationships between reproductive factors and breast cancer risk across various molecular subtypes.
  • Analyzed data from 42,922 women aged 40-79 after excluding the first year of follow-up.
  • Classified breast cancer cases by estrogen and progesterone receptor status.
  • Utilized cause-specific Cox proportional hazards models to estimate hazard ratios for associations.
  • Conducted subgroup analyses among Black women and used Fine-Gray subdistribution hazard models.
  • Multiparity is associated with reduced risk of luminal A-like and luminal B-like subtypes but increased risk of ER-/PR- tumors.
  • A later age at first childbirth correlates with higher risk of ER+/PR+ breast cancer and lower risk of ER-/PR- types.
  • Among Black women, multiparity shows a strong positive association with TNBC.

Structured PICO

Do reproductive factors influence the risk of specific breast cancer subtypes in women?

P
Population
42,922 women aged 40-79 years (69.2% Black) from the Southern Community Cohort Study.
I
Intervention
Reproductive factors (multiparity, age at first live birth)
O
Outcome
Breast cancer incidence by molecular subtypes (luminal A-like, luminal B-like, HER2-enriched, and triple-negative breast cancer)hard clinical

Reproductive factors such as parity and age at first birth have subtype-specific associations with breast cancer risk, highlighting etiologic heterogeneity.

Cite This Study

Gupta et al. (2026) studied this question. Multiparity (≥3 births) reduced the risk of luminal A-like (HR 0.74) and B-like (HR 0.53) breast cancers, but increased the risk of ER-/PR- disease (HR 1.71).

synapsesocial.com/papers/69d1fd4ea79560c99a0a3380https://doi.org/10.1158/1538-7445.am2026-2343
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