Propensity score to evaluate prognosis in pregnancy-associated breast cancer: Analysis from a French cancer network

Abstract Purpose To compare the prognosis of pregnancy associated breast cancer occurring during pregnancy (BCP) to non-pregnancy associated breast cancers (non-BCP) in young women managed at a national expert center. Methods Retrospective cohort study of a prospective database using propensity score matching (PSM) analysis with known prognostic factors. Results We analyzed data of 49 patients with BCP and 104 with non-BCP diagnosed between 2002 and 2017 at Tenon University Hospital (Paris, France). The BCP tumors were often locally advanced (lymph node metastases in 59%), of high grade (55%) and highly proliferative (67% with Ki67 ≥ 20%). After PSM, breast cancer-free survival (p = 0.45) and breast cancer specific survival (p = 0.81) were similar in the two groups. The recurrence rate was 12% vs 18% (p = 0.45) and the death rate was 6% vs 8% (p = 0.74) for the BCP and non-BCP groups, respectively. No difference in recurrence type was observed between the groups (p = 0.60). Conclusions After PSM for known prognostic factors, the prognosis of BCP patients did not differ from that of young patients with non-BCP.