Patients diagnosed with breast cancer within 10 years of postpartum depression have an increased risk for metastatic disease, according to results from a recent study by Erica T. Goddard, PhD, Public Health Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, Washington, and colleagues (JAMA Network Open. 2019;2[1]:e186997).

“In women 45 years or younger, breast cancer diagnosis after childbirth increases the risk for metastasis and death, yet limited data exist to define this window of risk and associated prognostic factors,” they said.

Thus, Dr Goddard and colleagues set out to determine the window of elevated risk for metastasis following a postpartum breast cancer diagnosis, and any prognostic factors associated with the increased risk.

They used data from the Colorado Young Women’s Breast Cancer Cohort to conduct a multicenter study of 701 women diagnosed with stage I to III invasive breast cancer between January 1, 1981, and December 31, 2014. The mean age at diagnosis was 37.9 years; data were analyzed from July 1, 2017, to September 30, 2017.

The primary end point of the study was distant metastasis–free survival. Dr Goddard and colleagues defined primary exposures as childbirth, time between most recent childbirth and breast cancer diagnosis, and time between diagnosis and disease metastasis.

According to the findings, women diagnosed with breast cancer within 10 years of parturition had an increased risk for metastasis, particularly if they had stage I or II disease. In women diagnosed with breast cancer within 10 years of a completed pregnancy that was estrogen receptor (ER)-positive, distant metastasis–free survival was similar to that of nulliparous patients with ER-negative cancer.

In addition, women with ER-negative postpartum breast cancer had further reduced metastasis-free survival. Of note, increased lymphovascular invasion and lymph node involvement were associated with postpartum breast cancer.

“This study suggests that patients with a PPBC diagnosis within 10 years of the most recent completed pregnancy have an increased risk for development of metastatic disease in stage I and II breast cancers of both ER-positive and ER-negative subtypes. These data provide further evidence that a PPBC diagnosis may represent a unique subtype of cancer that requires distinct clinical and translational research initiatives,”Dr Goddard and colleagues concluded.

“These observations should be confirmed in other cohorts of young women with breast cancer for determination of generalizability,” they added.—Hina Khaliq