New Combination Therapy of Atezolizumab and Trastuzumab Emtansine for Postoperative (Adjuvant) Treatment of HER2-Positive Breast Cancer

Adjuvant chemotherapy has long been a standard treatment for breast cancer. It begins after breast surgery and is used primarily when there is a high risk of the cancer returning. It is intended to reduce the risk of recurrence and thereby improve the long-term prognosis. If tumor cells have HER2 receptors on their surface (HER2-positive), trastuzumab emtansine is one of the drugs used, as both of these medications attack the tumor by binding to the HER2 receptors.

Atezolizumab is a so-called checkpoint inhibitor and thus belongs to a very new and highly effective class of cancer drugs. Atezolizumab attacks and destroys tumor cells through various mechanisms. Atezolizumab is already used as standard treatment for conditions such as lung cancer (NSCLC) and bladder cancer. Therefore, data on the drug’s safety and side effects are already available. In addition, a successful Phase II study of atezolizumab has already been conducted in breast cancer.

The goal of the Astefania study (Phase III study) is to test whether the additional administration of atezolizumab in breast cancer has an even better effect than trastuzumab emtansine alone—that is, whether it results in even fewer recurrences and improves the prognosis. Accordingly, the study has two arms: Patients will receive EITHER trastuzumab emtansine + atezolizumab (treatment arm) OR trastuzumab emtansine + placebo (control arm). Assignment is random (randomization), and neither the patient nor the doctor knows which study arm the patient is in (blinding).

Treatment consists of a total of 14 cycles, each lasting 21 days; after that, treatment within the study is completed. This is followed by a follow-up period to monitor whether and, if so, after how long a recurrence occurs. The follow-up period lasts for a maximum of approximately 6 years.