New Mothers Diagnosed with Breast Cancer May Be Higher Risk Despite Seemingly Good Prognosis

Past research has found that breast cancers diagnosed within five years of childbirth carry with them a substantially higher risk of becoming metastatic. A new study confirms these findings, showing that even when it seems the patient’s prognosis is good, new mothers may be higher-risk regardless.

Researchers at Oregon Health & Science University recently investigated the metastasis and death rates of breast cancer patients at different postpartum stages, compared with those who had not given birth. The findings, published in JAMA Network Open, show heightened risk of cancer spread and death up to five years after childbirth, despite stage or cancer subtype.

Dr. Pepper Schedin, senior author and professor of cell, developmental, and cancer biology at OHSU, says, “This has profound implications for prognosis. A postpartum diagnosis can move women who appear to have good prognosis into a high-risk category.”

Schedin’s team gathered their data from the Utah Population Database, which includes the state’s birth and death records, information from the Utah Cancer Registry, and inpatient and ambulatory records. Overall, data from 2,970 breast cancer patients were used. All had been diagnosed at age 45 or younger. Among them were 860 who had never given birth. The remaining patients were grouped into three categories: those who had been diagnosed within five years of childbirth, those who had received their diagnosis five to 10 years later, and those who were diagnosed more than 10 years after they had their last child.

The team found that for women less than five years out, the risk of metastasis and death from breast cancer were 50% higher compared with those who had not given birth. This was the case despite the stage at which diagnosis occurred or estrogen receptor status, which typically influence prognosis and help determine treatment. Generally, estrogen receptor-negative tumors are more aggressive, but for this group of women, the risk was the same even for estrogen receptor-positive tumors.

Schedin explains, “That does not fit with everything we thought we knew about ER-negative disease.”

Her past research may shed a light on why the risk is higher. In another study, it was discovered that a process that occurs after breastfeeding may be favorable to cancers. At the end of lactation, most of the milk-secreting cells undergo involution, which is programmed cell death. This leads to inflammation much like wound healing. In mice, the research team found it presented a favorable environment for tumors, while in human tissue, there was evidence that this process changes gene activity patterns in breast tissue that could lead tumors to spread.

Another study found that while it’s recovering from pregnancy and lactation, the liver provides a good destination for spreading cancer cells. The latest research mirrors that, finding that there were high rates of liver metastasis in those diagnosed within five years of childbirth.

Going forward, the team says considering postpartum status may help tailor treatment and allow for better understanding of the cancer’s prognosis. They also believe there’s the possibility to create treatments based on the differences in gene expression found in postpartum breast cancers.