Women diagnosed with breast cancer up to 10 years after giving birth have a higher risk of metastasis than childless women of the same age, a study says.
The study, “Association Between Postpartum Breast Cancer Diagnosis and Metastasis and the Clinical Features Underlying Risk,” was published in JAMA Network Open.
In a recent study, researchers showed that women who have had babies are significantly more likely to develop breast cancer, a risk that persists for more than 20 years. In women who develop breast cancer within five years of their last pregnancy — called postpartum breast cancer — the cancer also appears to have a worse prognosis, compared to women of the same age who never had children.
These are probably associated with the tissue reorganization that occurs in the breasts after childbirth with or without breastfeeding, and evidence suggests that the increased risk remains for more than five years after childbirth.
Therefore, researchers at the University of Colorado Cancer Center and Oregon Health & Science University performed a study to evaluate whether that prognosis extended to patients who had been diagnosed more than five years after giving birth.
They used the Colorado Young Women’s Breast Cancer Cohort to study 701 women under 45 with breast cancer stages I to III.
The investigators found that women who had been diagnosed up to 10 years after having their last child had increased risk of metastasis.
Particularly, women with stage I or II breast cancer had 3.5 to 5 times more risk of having their cancer spread than women who did not have children. This risk was independent of other risk factors such as age.
This tendency was observed regardless of estrogen receptor (ER) positivity, but for ER- positive tumors, the increased risk could persist even 15 years after childbirth.
“This is the first study to demonstrate that a postpartum breast cancer diagnosed up to 10 years after last childbirth can independently increase a woman’s risk for developing metastasis to other parts of the body,” Virginia Borges, MD, MMSc, Colorado University Cancer Center, and co-senior author of the study, said in a press release.
Women with postpartum breast cancer showed a higher presence of cancer in their lymph nodes and higher cancer invasion of the lymphovascular system.
“We have shown that the laying down of new lymph channels in breast tissue after childbirth and nursing may allow cancer cells to better travel and seed sites of metastasis; sure enough, the current work finds more women having cancer in their lymph nodes at diagnosis,” Borges said.
“These findings highlight the need to understand that postpartum breast cancer may represent a unique subtype of cancer that requires distinct care. All women know when they last gave birth, so this is a readily available, free piece of information that helps us identify young women at highest risk from their breast cancer,” Borges added.
Additionally, these data support that cancers should be considered postpartum at least 10 years after a woman’s last pregnancy.
“If we are aware of the increased risk, we can work toward finding the best means to overcome this risk and treat it appropriately,” Borges said.
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