Although cancer immunotherapy has revolutionized therapeutic regimens, only a fraction of patients responds to immune checkpoint blockade or adoptive cell transfer. It is thus highly important to make therapies more personalized by identifying the fraction of tumor reactive to bystander T cells that have infiltrated the tumor. Further, being able to selectively identify tumor reactive T cells, offers more targeted adoptive cell transfer by only reinfusing product that recognizes the tumor cells. Finally, identified tumor reactive TCRs may be used in personalized transgenic T cell receptor therapies.