The biological features and prognosis of breast cancer diagnosed during pregnancy: a case-control study

Breast cancer during pregnancy (BCP) is relatively rare and is associated with controversies about its biology and prognosis. Hence, we designed a case-control study to examine tumor features and outcome in a series of BCP patients diagnosed and treated in a single institution.

We identified 65 patients diagnosed with BCP and for each; we selected two non-pregnant breast cancer patients, who were matched for age, year of surgery, stage, and neoadjuvant chemotherapy. We then compared the differences in pathology, immunohistochemical features (ER, PR, HER2 and ki-67), disease-free (DFS) and overall survival (OS).

We did not find any significant differences in tumor characteristics between the two groups. However, at a median follow-up of four years, BCP patients had an inferior DFS (HR 2.3; 95% CI 1.3-4.2), after adjustment for possible confounding covariates. No difference in OS was observed. However, upon restricting the analysis to patients who did not receive neoadjuvant chemotherapy, patients with BCP had inferior OS as well (HR 2.6; 95% CI 1.0-6.5). No association between induction of abortion and prognosis was observed.

While we did not observe any differences in tumor features, BCP patients have poorer prognosis compared to age and stage-matched control. Further studies should try to elucidate reasons for such poor outcome.