This study is being done to answer the following question: Is the combination of T-DM1 and a newer drug tucatinib, better than usual treatment with T-DM1 alone at preventing human epidermal growth factor receptor 2 (HER2)-positive breast cancer from returning?
This study aims to find out if this approach is better or worse than the usual approach for human epidermal growth factor receptor 2 (HER2)-positive breast cancer.
- HER2-positive breast cancer
- Patients must have received neoadjuvant chemotherapy with one of the following regimens: THP, TMP, AC-TH(P); TCH(P); FAC-TH(P), or FEC-TH(P).
- Prior treatment must have consisted ≥ 6 cycles of chemotherapy and HER2-directed therapy, with a total duration of ≥ 12 weeks, including at least 9 weeks of preoperative taxane and trastuzumab with or without pertuzumab (or FDA-approved biosimilars).
- Prior receipt of T-DM1 in the neoadjuvant setting is not allowed.
- Not pregnant and not nursing
- No stage IV (metastatic) breast cancer
If you decide to take part in this study, you will either get treatment with T-DM1 and placebo (a pill that looks like the study drug but contains no medication) or T-DM1 and tucatinib, for up to 14 cycles, unless your breast cancer returns or the side effects become too severe. If the breast cancer returns while you are on the study, the treatment will be changed. You may also be told whether you were receiving T-DM1 and placebo or T-DM1 and tucatinib.
After you finish T-DM1 and placebo, or T-DM1 and tucatinib, your doctor will continue to follow your condition with clinic visits every 6 months for 10 years and watch you for side effects and for signs of breast cancer returning. This means you will keep seeing your doctor for 10 years after you are enrolled in the study.