The SAPPHO Study: Sequential Therapy With Curative Intent in de Novo HER2+ Metastatic Breast Cancer

The purpose of this study is to test the safety and effectiveness of a sequence of drugs (a Taxane plus Trastuzumab plus Pertuzumab followed by Trastuzumab Deruxtecan, followed by Tucatinib plus Ado-Trastuzumab Emtansine (T-DM1), followed by Trastuzumab plus Pertuzumab plus Tucatinib) in HER2+ Breast Cancer. The study will help investigators understand whether first intensifying therapy for a specific period and then stopping treatment is safe and effective for participants. The names of the study drugs involved in this study are: * Paclitaxel (a type of anti-microtubule agent) * Docetaxel (a type of anti-microtubule agent) * Nab-Paclitaxel (a type of anti-microtubule agent) * Trastuzumab (a type of IgG1 kappa monoclonal antibody) * Pertuzumab (a type of monoclonal antibody) * Trastuzumab Deruxtecan (a type of HER2-directed antibody drug conjugate) * Tucatinib (Tyrosine Kinase HER2 Inhibitor) * Ado-trastuzumab emtansine or T-DM1 (a type of HER2-targeted antibody-drug conjugate)