Breastfeeding May Help Women Survive Breast Cancer
NEW YORK (Reuters Health) – Breastfeeding may be associated with better prognosis and survival among breast cancer patients with certain intrinsic tumor subtypes, new research suggests.
“The findings from our study could potentially be another factor for the clinician to discuss with new (or soon-to-be new) moms regarding the decision to breastfeed,” Dr. Marilyn L. Kwan, of the Division of Research of Kaiser Permanente Northern California, in Oakland, told Reuters Health by email.
A woman’s breastfeeding history may affect her prognosis and survival by establishing a luminal tumor environment that has lower proliferative activity, Dr. Kwan and colleagues reported online April 8 in the Journal of the National Cancer Institute.
“Our findings not only lend further support to the established benefits of breastfeeding but also provide new insight into the mechanistic intricacies of lactation on breast cancer prognosis,” the authors wrote.
In 1,636 women from two prospective cohorts of breast cancer survivors, Dr. Kwan and colleagues used PAM50 gene expression assays to identify intrinsic tumor subtype (luminal A, luminal B, human epidermal growth factor receptor 2-enriched, or basal-like).
They obtained breastfeeding history from questionnaires. Medical record reviews documented 383 recurrences and 290 breast cancer deaths during a median follow up of nine years.
Using multinomial logistic regression, the researchers estimated the odds ratios between breastfeeding and tumor subtype. Using Cox regression, they estimated the hazard ratios for breast cancer recurrence or death.
Breast cancer patients with basal-like tumors were less likely to have breastfed in the past than those with luminal A tumors (OR=0.56), which tend to have the best prognosis of the four molecular subtypes.
Among all patients, ever breastfeeding was associated with lower risk of recurrence (HR=0.70), especially breastfeeding for six months or longer (HR=0.63, P for trend=0.01).
Associations for breast cancer death were similar. Among women with luminal A subtype, ever breastfeeding was associated with decreased risks of recurrence (HR=0.52) and breast cancer death (HR=0.52), but the authors found no significant associations among the other subtypes.
“The effects appeared to be limited to tumors with lower proliferation gene expression,” the researchers wrote.
Better outcomes were also possible in the women with luminal B and basal-like tumors, but the associations weren’t significant, the authors wrote.
“Few studies have examined if there is any effect of history of breastfeeding on breast cancer recurrence, and if the effect varies by the type of breast tumor that is initially diagnosed,” Dr. Kwan said.
“Breastfeeding has been shown to be possibly associated with reduced risk of developing breast cancer through hormonal mechanisms,” she added. “Therefore, the potential protective effect of breastfeeding on breast cancer recurrence among women who were already diagnosed seemed plausible.”
J Natl Cancer Inst 2015.
Please note articles posted on this site are only current as of the date of posting. Therefore, some information may be out of date at this time.