Breast Cancer Around Pregnancy Linked to Poorer Survival in Chinese Cohort

Women in China whose breast cancer is classified as pregnancy-associated faced a substantially higher risk of recurrence than women whose tumors arose outside that context, according to a single-center retrospective cohort study published in BMC Cancer. The study followed 382 women with stage I–III breast cancer and found that pregnancy-associated breast cancer, or PABC, was linked to poorer recurrence-free survival even after statistical adjustment for differences between the patient groups.

The researchers, led by Zhiyong Yu and colleagues, compared 185 PABC patients with 197 women who had non-pregnancy-associated breast cancer. Because the two groups differed in characteristics, the team also performed a propensity score matching analysis, pairing PABC patients with comparable non-PABC patients, which yielded 129 women in each matched group.

The biological profile of the tumors differed markedly between the groups. PABC tumors showed higher histological grades and more advanced T stages. The most striking molecular difference was in receptor status: 18.9 percent of PABC tumors were triple-negative breast cancer, an aggressive subtype that lacks estrogen receptors, progesterone receptors and HER2, compared with 8.1 percent of non-PABC tumors.

To explore whether reproductive history might relate to this molecular heterogeneity, the researchers used multinomial logistic regression to test associations between reproductive factors and tumor subtypes. Within the PABC group, a birth interval of less than five years was associated with higher odds of triple-negative disease relative to the luminal subtype, with an adjusted odds ratio of 3.15 and a 95 percent confidence interval of 1.15 to 8.64.

Lactation showed the opposite pattern. Women with PABC who had breastfed for one to less than two years had lower odds of triple-negative tumors compared with those who breastfed for two years or more, with an adjusted odds ratio of 0.22 and a 95 percent confidence interval of 0.08 to 0.64. The authors note, however, that these analyses were exploratory, and neither the birth interval nor the lactation association remained statistically significant after correction for multiple comparisons using the false discovery rate method, a statistical safeguard against false positives.

The survival findings were more robust. In the full cohort, PABC was associated with poorer recurrence-free survival, with an adjusted hazard ratio of 3.27 and a confidence interval of 1.28 to 8.40. In the propensity-matched cohort, designed to better balance the groups, the association persisted, with an adjusted hazard ratio of 3.64 and a confidence interval of 1.08 to 12.31, though the wide interval reflects the reduced sample size of 129 patients per group.

Not every factor influenced outcomes. Within the PABC group, birth interval was not significantly associated with recurrence-free survival, suggesting that the timing of recent childbirth may relate to tumor biology without independently predicting relapse in this cohort. The researchers analyzed recurrence-free survival using Kaplan–Meier estimates to compare survival curves over time and Cox proportional hazards models to adjust for covariates.

The authors caution that the findings should be confirmed in larger prospective cohorts. The associations between reproductive factors, such as lactation duration and birth interval, and molecular subtypes of PABC require verification in studies designed to test these relationships directly. For now, the study offers a detailed statistical picture of a clinically challenging patient population and a foundation for the larger investigations that would be needed to establish these associations more firmly.

Subject of Research: Associations between reproductive factors, molecular subtypes and prognosis in pregnancy-associated versus non-pregnancy-associated breast cancer

Article Title: Prognosis and associations between reproductive factors and molecular subtypes in Chinese women with pregnancy-associated and non-pregnancy-associated breast cancer: a retrospective cohort study

Article References: Li, J., Sun, L., Liu, Z., Li, C., Liu, X., & Yu, Z. (2026). Prognosis and associations between reproductive factors and molecular subtypes in Chinese women with pregnancy-associated and non-pregnancy-associated breast cancer: a retrospective cohort study. BMC Cancer. https://doi.org/10.1186/s12885-026-17221-6

Image Credits: AI Generated

DOI: 10.1186/s12885-026-17221-6

Keywords: pregnancy-associated breast cancer, triple-negative breast cancer, recurrence-free survival, retrospective cohort study, lactation, birth interval, molecular subtypes, propensity score matching, Chinese women, breast cancer prognosis, Prognosis, associations