Sacituzumab Govitecan in Primary HER2-negative Breast Cancer

Neoadjuvant chemotherapy (NACT) allows monitoring of tumor response to treatment and a pathological complete response (pCR) is associated with superior survival. This association is strongest in the most aggressive subtype, i.e. in patients with triple-negative breast cancer (TNBC). Patients with TNBC not achieving a pCR have a 5-year event free survival rate of about 50%. The association between pCR and prognosis is less pronounced in HR-positive/HER2-negative patients. However, the CPS+EG scoring system for prognosis after neoadjuvant chemotherapy, taking into account clinical stage, post treatment pathological stage, estrogen receptor status and grade, leads to an improved estimate of prognosis allowing to select patients at high risk of relapse for post-neoadjuvant therapy. Patients with TNBC not achieving a pCR as well as those with HR-positive/HER2-negative tumors and a CPS+EG score of 3 or 2/ypN+ are at high risk of relapse, warranting additional experimental therapies after NACT.

There is proof of concept, that post-neoadjuvant therapy can significantly improve survival. First data was provided by the CREATE X trial, randomizing patients with residual tumor after neoadjuvant chemotherapy to either capecitabine or observation. CREATE X included HER2-negative patients and demonstrated a significant improvement in disease-free survival (DFS) and overall survival (OS) in the overall population, which was confined to the TNBC subgroup.

Recently, the randomized post-neoadjuvant phase III KATHERINE study demonstrated an improved invasive disease-free survival in HER2-positive patients without pCR after trastuzumab +/- pertuzumab treated postoperatively with T-DM1, an antibody-drug-conjugate compared to trastuzumab.

Sacituzumab govitecan has demonstrated unprecedented activity in heavily pretreated patients with metastatic triple-negative and HR-positive/HER2-negative breast cancer, even after prior immune-checkpoint inhibitors or CDK4/6 and mTOR inhibitors. Based on the results of the phase I/II study, sacituzumab govitecan was granted a breakthrough therapy designation for the treatment of patients with advanced or metastatic TNBC who have received at least two previous lines of treatment for metastatic disease. The efficacy of sacituzumab govitecan in advanced TNBC was confirmed in the phase III ASCENT trial. Based on this study, sacituzumab govitecan received regular approval. Additionally, the TROPiCS-02 study showed an improvement in progression-free survival and OS over single-agent chemotherapy and a manageable safety profile in patients with heavily pre-treated HR-positive/HER2-negative endocrine-resistant, unresectable locally advanced or metastatic BC.