# Lactation on Breast Tumorigenesis

> **NIH NIH R01** · BAYLOR COLLEGE OF MEDICINE · 2024 · $497,126

## Abstract

Epidemiological studies have demonstrated that a first birth before age 25 lowers breast cancer (BCa) risk, while a
first birth after age 35 increases BCa risk. This age-dependent impact of first birth on BCa risk is generally
attributed to the pregnancy itself, with much less consideration for the lactation that often ensues. In young women,
evidence is strong that both pregnancy itself and lactation decrease BCa risk. However, the relative contribution of
pregnancy vs. lactation to increased BCa risk associated with a late-age reproduction has not been studied
rigorously, either epidemiologically or experimentally. Lactation itself at any age is assumed to be beneficial to both
mothers and infants, and is encouraged. However, our preliminary data suggest the hypothesis that lactation
instigates preexistent early lesions to progress to cancer. Given the increasingly large population of women who
choose to delay their first pregnancy to age 35 or older when the chance of having accumulated early lesions is
heightened, our hypothesis, if proven, has important and immediate implications for these women and especially
for women have been diagnosed with atypia. They can use this knowledge to make informed decisions regarding
whether and how long they will breastfeed. We will test this hypothesis and study the underlying molecular
mechanism by pursuing three aims: Specific Aim 1. To further elucidate the impact of pregnancy vs. lactation on
breast cancer risk of preexistent mammary early lesions. Specific Aim 2. To investigate how lactation modulates
the progression path of precancerous lesions. Specific Aim 3. To further elucidate lactation-induced changes in
precancerous lesions.

## Key facts

- **NIH application ID:** 10830427
- **Project number:** 5R01CA271588-02
- **Recipient organization:** BAYLOR COLLEGE OF MEDICINE
- **Principal Investigator:** Yi Li
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $497,126
- **Award type:** 5
- **Project period:** 2023-05-01 → 2028-04-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10830427

## Citation

> US National Institutes of Health, RePORTER application 10830427, Lactation on Breast Tumorigenesis (5R01CA271588-02). Retrieved via AI Analytics 2026-05-26 from https://api.ai-analytics.org/grant/nih/10830427. Licensed CC0.

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