Journal: NPJ breast cancer
This pooled, retrospective analysis combined national cohorts from Sweden and the Netherlands to compare breast cancer diagnosed during pregnancy with breast cancer in age- and calendar year–matched non-pregnant controls.
Key points:
- Design: Harmonized data from two national PrBC cohorts (1990s–2020s) were pooled. Each pregnant patient was matched to three non-pregnant controls per country. Non-parametric tests assessed clinicopathologic differences; fixed-effect meta-analysis with stepwise multivariable Cox models evaluated overall survival.
- Trimester differences:
- First trimester: PrBC cases were broadly similar in tumor characteristics to non-pregnant controls.
- Second and third trimesters: PrBCs showed distinctly more aggressive features than controls, including:
- Higher frequency of triple-negative subtype
- Higher histologic grade
- More advanced stage at diagnosis
- Survival:
- Overall survival for PrBC patients was worse than for matched non-pregnant controls.
- This survival disadvantage persisted even after adjustment for tumor characteristics and treatment.
- The negative impact on survival was most pronounced for diagnoses in the second and third trimesters, although the association lost statistical significance after full multivariable adjustment.
- Interpretation:
- The combination of more aggressive tumor profiles and persistently worse outcomes supports the concept that pregnancy-related, trimester-specific biological factors may influence tumor behavior and survival in breast cancer diagnosed during pregnancy.