Clinical and Pathological Characteristics and Prognosis of Breast Cancer During Pregnancy and Postpartum: A Multicenter Retrospective Study.

purposeThe prognostic impact of the interval between the most recent childbirth and breast cancer diagnosis remains insufficiently defined, particularly when breast cancer diagnosed during pregnancy (PrBC) is distinguished from postpartum breast cancer (PPBC). In this multicenter Chinese cohort, we aimed to validate and extend prior observations regarding the association between time since recent childbirth, clinicopathological features, and outcomes.

methodsThis multicenter retrospective cohort study included 12 453 patients aged 18-55 years with stage I to IV breast cancer for descriptive analyses; stage-restricted sub-cohorts were used for specific survival and modeling analyses as described below. These patients were diagnosed at three hospitals from July 1989 to June 2023, followed up until November 2023. The main exposures were diagnoses during pregnancy or the interval between the most recent childbirth and the diagnoses. The two primary outcomes assessed were disease-free survival (DFS) and breast cancer-specific death (BCSS). Cox proportional hazard models were employed to examine associations between exposures and outcomes. A nomogram using the least absolute shrinkage and selection operator (LASSO) penalty for variable selection. Model performance was evaluated using area under curve (AUC), decision curve analysis (DCA) curves and calibration.

resultsAmong 12 453 patients, 113 (0.9%) were diagnosed during pregnancy and 12 340 after childbirth. Patients diagnosed within 5 years after childbirth showed more aggressive clinicopathological characteristics, including larger tumors, more lymph node metastasis, and a higher Ki67 index. In contrast, results for PrBC should be interpreted cautiously because of the small sample size and potential treatment-related confounding. The poor prognosis of PPBC is potentially linked to an increased risk of liver and brain metastases. Multivariate analysis indicates that a short interval between childbirth and diagnosis is an independent risk factor for breast cancer prognosis. Predictors included in the nomogram were time interval between childbirth and diagnosis of breast cancer, T stage, N stage, and pathological subtype. The AUCs for 1-, 3-, and 5-year DFS prediction were 0.819, 0.767, and 0.731 in the training cohort and 0.818, 0.748, and 0.735 in the validation cohort.

conclusionPatients diagnosed with PPBC within 10 years after their most recent pregnancy, particularly within 5 years, had increased risks of recurrence, metastasis, and mortality.