After decades of development in the shadow of traditional
cancer treatment,
immunotherapy has come into the spotlight. Treatment of metastatic
tumors with
monoclonal antibodies to T cell checkpoints like programed cell death 1 (PD-1) or its
ligand, (PD-L1), have resulted in significant clinical responses across multiple
tumor types. However, these
therapies fail in the majority of patients with solid
tumors, in particular those who lack PD1(+)CD8(+) tumor-infiltrating lymphocytes within their
tumors. Intratumoral "in situ vaccination" approaches seek to enhance immunogenicity, generate
tumor infiltrating lymophcytes (TIL) and drive a systemic anti-
tumor immune response, directed against "unvaccinated," disseminated
tumors. Given the emerging picture of intratumoral
immunotherapy as safe and capable of delivering systemic efficacy, it is anticipated that these approaches will become integrated into future multi-modality
therapy.