Combined Antiangiogenic and Mammalian Target of Rapamycin Inhibitor Targeted Therapy in Metaplastic Breast Cancer Harboring a PIK3CA Mutation

Metaplastic breast cancer (MpBC) is an extremely rare breast cancer subtype, characterized by a heterogeneous phenotype. MpBC aggressive biology is attributed to its stem cell-like characteristics. Since these tumors are largely chemoresistant, novel targeted therapies should be explored. Herein, we report the clinical course of a 59-year-old African American woman with MpBC with a PIK3CA mutation in codon 545, exon 10 (GAG to AAG; p.Glu545Lys) and a TP53 mutation in codon 286, exon 8 (GAA to AAA; p.Glu286Lys). The same mutations were observed in the primary and secondary sites. The patient was treated with a molecularly matched therapy using a combined antiangiogenic and mammalian target of rapamycin kinase inhibitor strategy that included liposomal doxorubicin, bevacizumab, and temsirolimus. Partial remission was achieved. In this report, the scientific rationale underlying the activity of this combination was explored. In conclusion, patients may benefit from being offered molecular profiling early during the course of the disease to receive a therapy guided accordingly.