Addressing hepatic siphoning to enhance immunotherapy efficacy in veterans

Immune checkpoint inhibitors have revolutionized the care of patients with metastatic non-small cell lung cancer (NSCLC). Unfortunately, not all patients benefit from this therapy, and rational combinatorial strategies to enhance immune checkpoint inhibitors (ICI) efficacy in therapy non-responders are needed. We and others have shown that patients with liver metastases derive limited clinical benefit from ICI across a wide variety of disease types. In preclinical models, we discovered that liver metastases cause anti-PD-L1 resistance by siphoning tumor-specific T cells from systemic circulation. Within the liver, activated antigen-specific CD8+ T cells undergo apoptosis. Consequently, liver metastases create a systemic immune desert in preclinical models. Similarly, patients with liver metastases have reduced peripheral T cell numbers and diminished tumoral T cell diversity and function. In preclinical models, liver-directed radiotherapy eliminates immunosuppressive hepatic macrophages, increases hepatic T cell survival, and reduces hepatic siphoning of T cells. The central hypothesis of this proposal is that liver SBRT can enhance CPP therapy non-responders in NSCLC patients with liver metastases. In Aim 1, we will conduct a Phase IB clinical trial establishing the feasibility of delivering multi-target liver SBRT following the first cycle of carboplatin, pembrolizumab, and pemetrexed (CPP) in metastatic NSCLC patients with liver metastases. Up to four liver metastases will be targeted. In Aim 2, we will determine whether liver SBRT combined with ipilimumab and nivolumab modulates the hepatic and systemic immune microenvironment in NSCLC patients with liver metastases. The completion of these aims will assess the feasibility of ablating liver metastases with SBRT in combination with chemoimmunotherapy and deepen our understanding of the contribution of hepatic immune tolerance mechanisms in patients. The ultimate goal of this work is to test rationally-developed combinatorial treatment approaches in hopes of improving the care of NSCLC patients.