Local sinonasal and regional nodal effects of lymph node irradiation in a pilot study of dogs with naturally occurring sinonasal tumors.

Abstract

Head and neck cancer patients with high risks for regional metastasis receive radiation therapy targeted to their primary tumor and regional lymph nodes (RLN). RLN irradiation may alter cancer immunity. We investigate the impact of RLN irradiation in a pilot study of dogs with sinonasal tumors undergoing stereotactic body RT (SBRT). We hypothesized that RLN irradiation would reduce effector lymphocyte populations in the local microenvironment and RLNs following SBRT compared to dogs treated with SBRT targeted to the tumor alone. Previously, we demonstrated that RLN irradiation resulted in decreased populations of local CD4 and CD8 T cells following SBRT compared to dogs whose RLNs were spared. In this expanded study, the effects of RLN irradiation on local sinonasal cytokines and RLN tissue are presented. Dogs with sinonasal tumors were treated with SBRT targeted to the tumor alone or tumor + RLNs. The local microenvironment was serially sampled with nasal lavage and RLNs were removed and analyzed two weeks post-SBRT. Local sinonasal cavity cytokine levels increased in dogs whose RLN were spared from SBRT whereas cytokine levels from dogs treated with RLN irradiation did not. At two weeks post-treatment, multiplex immunofluorescence imaging revealed global increases in DNA damage, apoptosis, and density of dendritic cells in irradiated RLN compared to spared. Transcriptomic analysis of the RLN tissues two-weeks post-treatment indicated that RLN irradiation led to tissue microenvironmental immunomodulation and activation of cell death and damage pathways, whereas RLNs spared from RT had expression associated with effector T cell populations, regulation of immune cell migration and adhesion, and responses to stimuli and developmental pathways. We expand upon our previous canine results, which demonstrate that RLN irradiation can reduce local effector lymphocyte populations, and provide preliminary evidence that RLN irradiation can alter local cytokine shifts, as well as induce apoptotic and damage responses within irradiated nodal tissues.