Immunotherapy of brain metastases: breaking a "dogma"

Until very few years ago, the oncology community dogmatically excluded any clinical potential for immunotherapy in controlling brain metastases. Therefore, despite the significant therapeutic efficacy of monoclonal antibodies to immune check-point(s) across a wide range of tumor types, patients with brain disease were invariably excluded from clinical trials with these agents. Recent insights on the immune landscape of the central nervous system, as well as of the brain tumor microenvironment, are shedding light on the immune-biology of brain metastases.Interestingly, retrospective analyses, case series, and initial prospective clinical trials have recently investigated the role of different immune check-point inhibitors in brain metastases, reporting a significant clinical activity also in this subset of patients. These findings, and their swift translation in the daily practice, are driving fundamental changes in the clinical management of patients with brain metastases, and raise important neuroradiologic challenges. Along this line, neuro-oncology undoubtedly represents an additional area of active investigation and of growing interest to support medical oncologists in the evaluation of clinical responses of brain metastases to ICI treatment, and in the management of neurologic immune-related adverse events.Aim of this review is to summarize the most recent findings on brain metastases immunobiology, on the evolving scenario of clinical efficacy of ICI therapy in patients with brain metastases, as well as on the increasing relevance of neuroradiology in this therapeutic setting.

The Italian Network for Tumor Bio-Immunotherapy (NIBIT) Foundation: ongoing and prospective activities in immuno-oncology

The ongoing revolution in cancer immunotherapy stems from the knowledge that distinct immune-checkpoints regulate the physiological crosstalk between and among immune cells by delivering inhibitory or activating signals. These notions, and the availability of mAb directed to diverse immune-checkpoint molecules, have led to a significant clinical improvement in cancer treatment. In this scenario, further achievements are undoubtedly to be expected from the contribution of novel, proof-of-principle clinical trials designed to explore the therapeutic efficacy of new immunotherapy-based combinations and treatment sequences. Along these lines, the clinical translation of pre-clinical evidence generated by non-profit research entities is likely to provide a significant contribution to gaining new insights that will further boost the field of cancer immunotherapy. To pursue this goal, and to provide comprehensive educational programs in immune-oncology (I-O), several national and global networks have been revitalized or newly established in recent years. This rapidly evolving scenario led the Board of Directors of the Italian Network of Tumor Bio-Immunotherapy (NIBIT) to establish the NIBIT Foundation. This Focused Research Review summarizes the main ongoing and prospective I-O activities of the NIBIT Foundation.

Immune Checkpoint Inhibitors for the Treatment of Central Nervous System (CNS) Metastatic Disease

While the CNS has long been viewed as an immune-privileged environment, a paradigm shift in neuro-immunology has elevated the role of systemic immunotherapy for the treatment of metastatic disease. Increasing knowledge regarding the presence of a CNS lymphatic system and the physical and biochemical alteration of the blood brain barrier (BBB) by the tumor microenvironment suggests immune cell trafficking in and out of the CNS is possible. Emerging clinical data suggest immune checkpoint inhibitors (ICIs) can stimulate T cells peripherally to in turn have anti-tumor effects in the CNS. For example, anti-programmed cell death-1 (PD-1) monotherapy with pembrolizumab has shown intracranial response rates of 20-30% in patients with melanoma or non-small cell lung cancer (NSCLC) brain metastases. The combination of nivolumab and ipilimumab [anti-PD-1 and anti-cytotoxic T-lymphocyte-associated protein 4 (CTLA-4)] showed an intracranial response rate of 55% in patients with melanoma brain metastases. More data are needed to confirm these response rates and to determine mechanisms of efficacy and resistance. While local therapies such as stereotactic radiosurgery (SRS), whole-brain radiation therapy (WBRT), and surgery remain current mainstays, ICIS offer potential decreased neurotoxicity. This review summarizes the biological rationale for systemic immunotherapy to treat CNS metastatic disease, existing clinical data on ICIs in this setting and ongoing clinical trials exploring areas of unmet need.

Immunotherapy targeting immune check-point(s) in brain metastases

Immunotherapy with monoclonal antibodies (mAb) directed to different immune check-point(s) is showing a significant clinical impact in a growing number of human tumors of different histotype, both in terms of disease response and long-term survival patients. In this rapidly changing scenario, treatment of brain metastases remains an high unmeet medical need, and the efficacy of immunotherapy in these highly dismal clinical setting remains to be largely demonstrated. Nevertheless, up-coming observations are beginning to suggest a clinical potential of cancer immunotherapy also in brain metastases, regardless the underlying tumor histotype. These observations remain to be validated in larger clinical trials eventually designed also to address the efficacy of therapeutic mAb to immune check-point(s) within multimodality therapies for brain metastases. Noteworthy, the initial proofs of efficacy on immunotherapy in central nervous system metastases are already fostering clinical trials investigating its therapeutic potential also in primary brain tumors. We here review ongoing immunotherapeutic approaches to brain metastases and primary brain tumors, and the foreseeable strategies to overcome their main biologic hurdles and clinical challenges.