Prognosis of pregnancy-associated breast cancer: A meta-analysis of 30 studies

Background: Pregnancy-associated breast cancer (PABC) is relatively rare with considerable controversy regarding its prognosis. Patients & methods: Two of the authors independently performed a literature search with no date or language restrictions. Eligible studies were control-matched, population-based and hospital-based studies that addressed the outcome of patients diagnosed during pregnancy or 1-year afterwards. The primary and secondary end-points were overall and disease-free survival respectively. Pooling of data was done using the random effect model. Results: 30 studies were included in this meta-analysis (3,628 cases and 37,100 controls). PABC patients had a significantly higher risk of death compared to those with non-pregnancy-related breast cancer (pooled hazard ratio (pHR): 1.44; 95% CI [1.27-1.63]). The same results were encountered on restricting the analysis to HRs of multivariate analyses (pHR: 1.40 [1.17-1.67]). A clearer trend of poorer outcome was seen in those diagnosed postpartum (pHR: 1.84; 95% CI [1.28-2.65]) than those diagnosed during pregnancy (pHR: 1.29; 95% CI [0.74-2.24]). DFS analysis showed a significantly higher risk of relapse associated with PABC as well (pHR: 1.60 [1.19-2.16]). Conclusion: Our results show that PABC is independently associated with poor survival particularly those diagnosed shortly post-partum. This underscores a possible impact of the pregnant breast microenvironment on the biology and consequently the prognosis of these tumors.