Targeted therapy for breast cancer during pregnancy: A case report and literature review

Introduction: Breast cancer is the most common malignancy diagnosed during pregnancy, with HER2-positive subtypes posing particular therapeutic challenges due to the fetal risks associated with targeted therapies. Despite growing data, management decisions remain complex and often individualized. Case Report: We report the case of a 38-year-old woman diagnosed with HER2-positive, hormone receptor-positive invasive ductal carcinoma of the breast. We discovered a pregnancy at 25 weeks of gestation, while neoadjuvant chemotherapy, including trastuzumab and pertuzumab, had already been initiated. The first ultrasound revealed anhydramnios with unremarkable fetal renal morphology. From the diagnosis, anti-HER2 therapy was discontinued, but the weekly paclitaxel was continued. At 33 weeks, severe renal and pulmonary hypoplasia were detected. However, partial reversal of anhydramnios was observed by 36 weeks. The patient delivered at 38 weeks a male infant with early respiratory distress and suspected pulmonary hypertension, but with preserved renal function. The infant was discharged in good condition. The mother achieved a complete pathological response and remains in remission one year after pregnancy diagnosis. Conclusion: The use of anti-HER2 therapy during pregnancy, particularly in the second and third trimesters, is associated with significant fetal risks. These risks may exhibit partial reversibility after drug cessation. Early pregnancy detection and individualized treatment planning are essential to optimize the maternal and neonatal outcomes.