THURSDAY, July 16, 2026 (HealthDay News) -- Postpartum breast cancer (PPBC) diagnosed within the first year postpartum has a significantly elevated 21-gene Oncotype DX Recurrence Score (RS), according to a study published online July 1 in npj Breast Cancer.
Shiliang Zhang, M.D., from the University of California, Los Angeles, and colleagues conducted a single-institution retrospective cohort study to examine the impact of postpartum status on the 21-gene Oncotype DX RS in hormone receptor-positive, human epidermal growth factor receptor 2-negative young women with breast cancer. Of 385 patients, 153, 62, and 170 were nulliparous, >10 years postpartum, and within 10 years postpartum, respectively.
The researchers found that compared with nulliparous patients, diagnosis within one year of childbirth was associated with a 13.2-point higher RS. The odds of RS category shift were increased in association with defining PPBC as within three years postpartum (odds ratio, 2.83). Differences in invasive disease-free survival (IDFS) associated with time since last childbirth did not result in significantly worse IDFS within the follow-up period in the context of contemporary adjuvant treatment, with patients diagnosed within three years postpartum more likely to receive chemotherapy, ovarian function suppression, and CDK4/6 inhibitors (89.0 percent in patients with PPBC up to three years versus 93.7 percent in all other patients).
"Our findings suggest that the years immediately following childbirth represent a unique biological window for some breast cancers," senior author Nimmi S. Kapoor, M.D., also from the University of California, Los Angeles, said in a statement. "Understanding why these tumors behave differently may help us better identify patients who need closer monitoring or more tailored treatment approaches."
Several authors disclosed ties to the biopharmaceutical industry.
