Tumors grow within a host tissue that both facilitates progression by supplying nutrients and growth factors, and inhibits it through physical constraints and immune surveillance. Transformed cancer cells are confronted with this innate and adaptive immune surveillance, and tumors that develop to become clinically apparent have evolved to evade the immune system. This complex ecological system may be tipped back in favor of effective immune surveillance and tumor regression through novel immunotherapeutic strategies, particularly when used in concert with focal cytotoxic agents such as radiotherapy.

We developed a multi-scale mathematical model framework to simulate local tumor-immune interactions as well as systemic distribution patterns of T cells activated locally in each metastatic site. We simulate focal radiotherapy-induced cytotoxicity and subsequent activation of an adaptive immune response, which may propagate systemically to cause regression of unirradiated metastases, known as the abscopal effect. We simulate concurrent anti-CTLA4 immunotherapy to investigate synergy.

Model simulations suggest that systemic distribution of locally activated T cells is dependent on (i) the anatomical distribution of metastatic sites, (ii) the tumor volume of each metastasis, (iii) the site of focal therapy, (iv) the local therapy protocol of immune activation, and (v) the timing of concurrent immunotherapy. We find that irradiation of different metastatic sites has different likelihoods of inducing systemic tumor regressions.

The developed framework can identify combination therapy protocols that optimally harness the synergy of focal therapy-induced immunity with immunotherapy, and identify optimum treatment targets on a per patient basis.

Citation Format: Jan Poleszczuk, Kimberly Luddy, Shari Pilon-Thomas, Jonathan Schoenfeld, Heiko Enderling. Personalizing the synergy of focal radiation and immunotherapy. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4016.