Pregnancies during and following trastuzumab (T) and/or lapatinib (L) in patients (pts) with HER2 positive (HER2+) early breast cancer (EBC): Analysis from the NeoALTTO (BIG 1 …

10065 Background: Limited data exist on the safety of using targeted agents in pregnant cancer pts. So far, only retrospective studies assessed the prognosis of pts having a pregnancy after prior EBC with no data in HER2+ pts. We aimed to evaluate the outcome of pregnancies occuring during or following T and/or L and the prognostic effect of having a pregnancy in HER2+ EBC pts. Methods: NeoALTTO and ALTTO were randomized phase 3 trials in HER2+ EBC pts. In both trials, pregnancy information was prospectively collected. Pregnancy outcomes were compared between pts unintentionally exposed to T and/or L during gestation (exposed group) and those who got pregnant following T and/or L completion (not-exposed group). In the ALTTO trial, disease-free (DFS) and overall survival (OS) of pregnant pts were compared to those of pts≤ 40 years without subsequent pregnancy with the Extended Cox Model …