Local Immunotherapy of Cancer: Innovative Approaches to Harnessing Tumor-Specific Immune Responses

Modern cancer immunotherapies represent a major shift in paradigm with respect to how we understand innate and adaptive responses to malignancy. Successful tumors co-opt normal immunosurveillance mechanisms by potent interactions between the tumor and local draining lymph nodes. Tumor cells mediate a complex and dynamic immunoediting procedure that results in increased vascular efflux into the draining lymphatics, an immunosuppressive microenvironment rich in regulatory T-lymphocytes, dysfunctional antigen presentation, and downregulation of normal effector lymphocyte responses. Our current approach to reversing this process for antitumor effect involves mainly systemic administration of immunotherapeutic agents, many of which have become standard of care in the management of a variety of cancers. Despite this, we are still learning how best to administer these drugs alone and in combination to maximize efficacy while minimizing adverse events. Increasing evidence suggests that comparable efficacy may be achieved by local administration of immunotherapies in the tumor or tumor-draining lymph nodes with substantially lower doses and better tolerability, even with combination therapy. Herein, we review the literature on intratumoral and intranodal immunotherapies in preclinical models and early-phase studies, with particular emphasis on approaches potentially suitable for translation to larger-scale clinical trials.