Survival in pregnancy-associated breast cancer patients compared to non-pregnant controls.

Background: Pregnancy-associated breast cancer (PABC) is a rare entity whose prognosis has previously been studied and is subject to controversy.

Methods: Survival of patients with PABC diagnosed between 2009 and 2021 with breast cancer during pregnancy or until 1 year after childbirth was compared with non-pregnant patients with breast cancer from the same period at La Paz University Hospital. Cox proportional hazards regression was used to compare disease-free (DFS) and overall (OS) survival between the groups, adjusting for grade and pathologic stage.

Results: Among the 89 included patients with breast cancer, 34 were diagnosed during pregnancy, and 55 were not pregnant. The pregnant patients were more likely to have grade 3 tumors (61.3% vs 37%, p = 0.023) and an advanced stage (pathologic stage III-IV: 44.1% vs 17.6%, p = 0.008). Median follow-up was 47 months for the pregnant group and 46 months for the control group. After adjustments for tumor grade and pathologic stage, OS was comparable between the groups (HR 2.03; 95% CI 0.61 to 6.79; P = 0.25).

Conclusions: The outcome of women diagnosed with PABC is comparable to young non-pregnant controls. However, it should be taken into account that PABC has a more aggressive phenotype.