Case studies highlighting the multiple facets of gastric cancer: one diagnosis, multiple approaches

Worldwide, gastric cancer is the fifth most prevalent cancer and third leading cause of mortality. Gastric cancer is a heterogenous disease and our understanding of this disease is rapidly expanding. Subsequently, the treatment landscape is also changing. Chemotherapy plus or minus trastuzumab for patients with human epidermal growth factor receptor 2 (HER2)-positive disease has been the main treatment option until recently. Notably, a role for immunotherapy is being defined. Current relevant biomarkers clinically utilized for treatment selection are HER2, DNA mismatch repair/microsatellite instability, and programmed death-ligand 1. It is anticipated ongoing research will identify clinically relevant biomarkers to assist in treatment decision-making and identify new drug targets, ultimately improving patient outcomes. In this chapter, we describe four patient cases that highlight the heterogenous nature of gastric cancer, also demonstrating that despite the poor prognosis of advanced gastric cancer, patients can achieve durable disease control.