Being breastfed in infancy linked to heightened risk for CRC; more research needed
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Key takeaways:
- Women who were breastfed for 9 months or more had a 36% increased risk for colorectal cancer.
- A significant link was found between being breastfed and increased risk for high-risk adenomas in younger women.
Being breastfed in infancy was associated with a 23% increased risk for colorectal cancer in adulthood, especially among women younger than 50 years, according to a study in Clinical Gastroenterology and Hepatology.
“A recent study, conducted with a cohort of half a million women in the U.K., reported an unexpected yet highly significant association between individuals who were breastfed as infants and an elevated risk of developing colorectal cancer,” Chen Yuan, ScD, an instructor in the department of medical oncology at the Dana-Farber Cancer Institute and Harvard Medical School, told Healio. “Because breastfeeding has become much more common in recent decades, these findings captured our attention and prompted us to further explore and validate these results in an independent cohort.”
Using data from 66,634 women (aged 46-93 years) in the Nurses’ Health Study (NHS) and 92,062 women (aged 27-68 years) in the Nurses’ Health Study II (NHSII), Yuan and colleagues prospectively investigated the association between a history of being breastfed and the risk for CRC and its precursor lesions.
During 3.5 million person-years of follow-up, researchers reported 1,490 incident cases of CRC, of which 1,142 included women from NHS (median age, 71 years) and 348 from NHSII (median age, 52 years). Having been breastfed was associated with an increased risk for CRC in both cohorts (HR = 1.21; 95% CI, 1.06-1.38 and HR = 1.31; 95% CI, 1.06-1.63, respectively) and, when combined, corresponded with a 23% increased risk.
“This association was found to be statistically significant, with a confidence interval of 10% to 38%,” Yuan said. “Importantly, we took great care to control for a wide range of early-life exposures and lifestyle factors during adulthood, including maternal exposures during pregnancy, to ensure the robustness of our findings.”
Compared with women who were not breastfed, those who were breastfed for 3 months or less had a 14% increased risk for CRC, which rose to 17% in those breastfed for 4 to 8 months and 36% in those breastfed for at least 9 months. Researchers also reported that being breastfed was associated with a 40% (95% CI, 16-68) increased risk for proximal colon cancer and a 17% (95% CI, –1 to 38) increased risk for distal colon and rectal cancer.
Among younger women from NHSII, Yuan noted a “significant association” between being breastfed and increased risk for high-risk adenomas — precursor lesions of CRC — among those younger than 50 years (OR = 1.46; 95% CI, 1.16-1.83).
When examining the link between being breastfed and risk for younger-onset CRC, researchers “consistently” reported an increased risk among women aged 55 years and younger (HR = 1.38; 95% CI, 1.06-11.8).
“Breastfeeding offers numerous advantages for both mothers and infants, which are likely to outweigh any potential heightened risk of CRC in adulthood,” Yuan said. “Our study should not be interpreted as discouraging breastfeeding.”
She continued: “Subsequent research should delve into the biological mechanisms underlying the association, including the role of the microbiome or other pathways. It is of utmost importance to elucidate the causes of the rise of young-onset colorectal cancer so that novel prevention and early detection strategies can be developed.”
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