How Breastfeeding May Help the Body Fight Breast Cancer

New research from Australia’s Peter MacCallum Cancer Centre and featured in “New Scientist” offers fresh insight into how breastfeeding may help protect against breast cancer. An article available under accelerated article preview, “Parity and lactation induce T cell mediated breast cancer protection,” is available from the journal Nature.

While it’s long been known that breastfeeding is linked to a reduced risk of breast cancer—estimated at a 4.3% lower risk for every year of breastfeeding—the biological reasons weren’t fully understood until now.

Scientists found that women who have breastfed have higher levels of specialized immune cells, known as CD8+ T cells, in their breast tissue. These “local guards” can remain for decades—sometimes up to 50 years—acting as long-term defenders that identify and destroy abnormal or potentially cancerous cells.

The research team confirmed the finding in animal studies, showing that mice that completed a full cycle of pregnancy and lactation developed these same immune cells and had significantly slower tumor growth when exposed to aggressive breast cancer cells. When the T cells were removed, tumors grew much faster.

Further analysis of clinical data from more than 1,000 women with triple-negative breast cancer showed that those who had breastfed had higher CD8+ T cell density in their tumors and lived longer overall, even after accounting for age and other risk factors.

Researchers believe these cells may form during breastfeeding to protect against infections like mastitis, offering a possible explanation for breastfeeding’s lasting cancer-protective effects.

While the findings add an important piece to the puzzle of breast cancer prevention, experts emphasize that breastfeeding is a personal choice and not always possible. Still, this study helps scientists better understand how the immune system’s “memory” of breastfeeding might inspire new prevention or treatment strategies in the future.

Read the full article here.