Neo-antigen specific T cell responses indicate the presence of metastases before imaging

Non-small cell lung cancer (NSCLC) causes 19% of all Australian cancer deaths, with a 5-year survival post-resection of around 60%. Post-operative recurrence is due to metastases that were undetectable pre-operatively, or growth of microscopic locoregional residual disease. However, post-operative imaging modalities typically only detect more advanced tumours; where PET-CT has a detection limit of 6-7 mm. Detection of small deposits of lung metastatic disease is of importance in order to facilitate early and potentially more effective treatment. In this study, in a murine model of lung metastatic disease, we explore whether neo-antigen specific T cells are a sensitive marker for the detection of lung cancer after primary tumour resection. We determine lung metastatic disease by histology, and then compare detection by PET-CT and neo-antigen specific T cell frequency. Detection of lung metastatic disease within the histology positive group by PET-CT and neo-antigen specific T cell frequency were 22.9% and 92.2%, respectively. Notably, neo-antigen specific T cells in the lung draining lymph node were indicative of metastatic disease (82.8 ± 12.9 spots/10⁵ cells; mean ± SE), compared to healthy lung control (28.5 ± 8.6 spots/10⁵ cells; mean ± SE). Potentially, monitoring tumour neo-antigen specific T cell profiles is a highly sensitive method for determining disease recurrence.