STOP-HER2: Stopping Trastuzumab in HER2+ MBC

This is a single arm, phase II study of cessation of anti-HER2 systemic therapy in exceptional responders with HER2-positive metastatic breast cancer (MBC), defined as individuals free of disease progression after at least 3 years of first-line treatment. This research study will include two different groups (cohorts) of patients. Those not wanting to stop anti-HER2 maintenance treatment will be included in a non-randomized, observational cohort (cohort 1). Those willing to stop maintenance anti-HER2 treatment you will be included in cohort 2. This study is trying to understand whether blood samples that may contain traces of DNA from cancer, known as "circulating tumor DNA" or "ctDNA" are able to help identify which patients can successfully stop treatment without a change in their cancer. The research study procedures include: an initial screening phase followed by periodic visits with blood work, questionnaires, and body scans. It is expected that about 82 people will take part in this research study (52 in cohort 2 (stopping treatment), 30 in cohort 1 (continuing treatment). This study is expected to last 1 year with 10 years of follow up. The Susan G. Komen Foundation, the Gateway for Cancer Research - both nonprofit foundations supporting cancer research - and the National Institutes of Health are supporting this research study by providing funds. This study is also being supported by Johns Hopkins University on behalf of the Translational Breast Cancer Research Consortium (TBCRC). The TBCRC is a group of academic medical centers across the United States that work together to conduct breast cancer research.