In the near future, important translational questions of clinical relevance will be adressed by studies currently in progress. On the one hand, the role of PD-L1 expression must be further understood, after it was found to be relevant in the use of atezolizumab in first-line therapy of patients with metastatic triple-negative breast cancer (TNBC). No association between efficacy and PD-L1 expression was found in a neoadjuvant study that included pembrolizumab in TNBC. The pathological complete response rate (pCR) was higher in both patient groups with and without PD-L1 expression when pembrolizumab was added to chemotherapy. Another future question is the identification of further patient groups in which efficacy of PARP inhibitors is seen, which are licensed for the pBRCA1/2 germline mutation. These include, for example, patients with mutations in other genes, which are involved in homologous recombination, or patients with tumours that show an abnormality in global tests of homologous recombination deficiencies (HRD tests). The question of whether a PARP inhibitor can be given and with which chemotherapy combination partners is currently being investigated in both breast and ovarian cancer. While the data on improved overall survival are being consolidated for the CDK4/6 inhibitors, knowledge of molecular changes during the therapy and during progression on the therapy is growing. Both the accumulation of PI3K mutations and also PTEN changes might play a part in planning subsequent therapies. This review article summarises these recent developments in breast cancer and in part also in ovarian cancer.
Keywords: BRCA1/2; CDK4/6; PARP; PD-L1; advanced breast cancer; immunotherapy; metastases; mutation testing; therapy.