Inhibition of epidermal growth factor receptor (EGFR) prior to the delivery of photodynamic therapy (PDT) can remarkably improve treatment efficacy in animal models of non-small cell lung cancer (NSCLC). Currently, clinical use of EGFR tyrosine kinase inhibitors (TKIs) for treatment of patients with NSCLC is limited to those with EGFR mutated disease. EGFR-TKI therapy is typically continued until time of disease progression since most patients eventually develop EGFR-TKI resistant disease. Here, we propose to use EGFR-TKIs as a brief, priming therapy for several days rather than as a daily continuous therapeutic. Importantly, as a priming therapy, we hypothesize that EGFR-TKI pretreatment will improve the therapeutic efficacy of PDT (and ionizing radiotherapy, XRT) through an innate immune response-dependent mechanism. Significantly, we posit that the use of EGFR-TKIs as a priming approach to stimulate innate immunity is relevant to patients with EGFR wild-type disease. However, its potential efficacy may not be apparent in the setting of daily continuous EGFR-TKI therapy due to suppression of innate and adaptive immunity by prolonged use of EGFR-TKIs. As a priming therapy, EGFR-TKIs could augment responses to PDT and XRT through multiple mechanisms that involve cooperation between the EGFR-TKIs and PDT or XRT to promote tumor-directed innate immunity. EGFR-TKIs may increase neutrophil activation in tumors receiving PDT or XRT, serving to increase vascular damage and/or stimulate other cells of the innate immune system, such as innate immune lymphocytes. Indeed, our published data show EGFR-TKI to increase vascular damage to PDT, and preliminary data demonstrate increases in tumor-localized neutrophil activation when PDT is preceded by EGFR-TKI (EGFR- TKI/PDT). Additionally, EGFR-TKIs and PDT or XRT may cooperatively increase numbers of innate immune lymphocytes and the immunologic visibility of target cells (e.g., tumor cells or tumor-associated endothelial cells) to these lymphocytes. In fact, in preliminary data the efficacy of EGFR-TKI/PDT is dependent on the innate immune lymphocytes NK and γδ T cells. We note that the role of γδ T cells in response to EGFR-TKI, notwithstanding combinations with PDT or XRT, is a novel area of investigation. Moreover, we uniquely investigate EGFR-TKI priming with proton XRT. Knowledge gained from this proposal will guide selection of a clinical approach to EGFR-TKI priming with radiation therapy, whether it be with PDT, photon XRT, or proton XRT. Toward this goal, we will address the following aims: Aim 1. To define the role of neutrophils in promoting vascular damage when PDT is preceded by EGFR-TKI. Aim 2. To ascertain how pretreatment with EGFR-TKI augments the response of innate immune lymphocytes to PDT-treated tumors. Aim 3. To establish the efficacy and innate immune effects of EGFR-TKIs combined with ionizing radiation therapies (photon and proton) and demonstrate appl...