Evaluating 6-months of HER2-targeted Therapy in Patients With HER2 Positive Early-stage Breast Cancer That Achieve a Pathological Complete Response to Neoadjuvant Systemic Therapy

The activity of trastuzumab in early-stage, HER2-positive breast cancer, has been demonstrated in many studies, with meta-analyses showing that in combination with a variety of chemotherapy backbones, trastuzumab reduces the risk of recurrence by nearly half, and death by a third. However, treatment with trastuzumab can result in cardiotoxicity, including heart failure, as well as the significant cost of treatment and the requirement for patients to attend the chemotherapy unit for treatment every 3 weeks for one year. Therefore there has been increasing interest in identifying which patients can safely have less treatment. The duration of adjuvant trastuzumab in early-stage breast cancer in the majority of studies was empirically set at 12 months, which became the de facto standard of care. Neoadjuvant treatment has become the new standard of care for patients with early-stage HER2-positive disease. While patients with residual disease benefit from further alternative treatment those with a pathological complete response (pCR) have an excellent outcome and are candidates for treatment de-escalation. The investigators therefore propose a real-world, single arm, multicentre trial evaluating 6 months of HER2 targeted therapy, for patients with early-stage, HER2 positive breast cancer, who achieve a pCR with upfront systemic chemotherapy and HER2 targeted therapy.