4.2.6 Targeted therapies and immunotherapy
The role of targeted therapies and immunotherapies is evolving. Trastuzumab in combination with chemotherapy is currently the only targeted drug shown to improve survival over chemotherapy alone in a subset of patients with HER2-positive metastatic adenocarcinoma involving the stomach or gastro-oesophageal junction. A few randomised studies also suggest modest benefit from immunotherapy in later disease stages (Janjigian et al. 2018; Kang et al. 2017). Recent trials have demonstrated improvement in survival and fewer adverse effects with anti-PDL1 immunotherapy either as monotherapy or in combination with chemotherapy in patients with tumours that have high expression of programmed cell death ligand 1 (PD-L1), with a combined positive score (CPS) ≥ 10, or deficient mismatch repair (dMMR)/high levels of microsatellite instability (MSI) (Bristol Myers Squibb 2020; Tabernero et al. 2019). However, apart from trastuzumab, immunotherapy is currently not reimbursed by the Pharmaceutical Benefits Scheme, and where possible patients should be encouraged to enrol in clinical trials.