Basket Study for Oligo-metastatic Breast Cancer

The study will include patients with HER2-positive breast cancer and 1- 3 distant metastatic lesions, all amenable for curative intervention. Patients will be stratified by prior therapy and ER expression. In the initial baskets patients with be treated with trastuzumab-deruxtecan. Patients are treated with T-DXd 5.4mg/kg on a three weekly (21 day) basis, with the goal of 16 cycles leading to a treatment period of year, including local treatment. The first 8 cycles of T-DXd are administered neo-adjuvant, and 8 cycles adjuvant, after completion of local treatment. The proposed M22BOL trial is based on an important knowledge gap for regarding breast cancer patients with 'oligo-metastatic' disease who are usually not included in clinical trials for patients with metastatic disease since loco-regional treatments (radiation, surgery) with curative intent is not allowed in clinical trials for metastatic breast cancer. Moreover, neo-adjuvant trial protocols for early breast cancer exclude patients with distant metastases that can be treated with curative intent. This basket trial evaluates T-DXd for oligo-metastatic breast cancer with the goal to induce deep responses and subsequently long-lasting disease remissions and potentially cure.