Abstract 533: The immune landscape in colon cancer and its changes after radiotherapy

Abstract

Abstract Background: The TRANSLATE project started in 2016 to test the immune effects on circulating immune cells and cytokines of metronomic Cyclophosphamide (CTX), daily low-dose IL-2 administered every other week, and radiotherapy (RT). The rationale is based on self vaccination induced by RT, T cells expansion by IL-2 treatment and selective Tregs down regulation by low dose cyclophosphamide administration. Materials/Methods: Treatment consisted of CTX 50/mg tab daily continuously until progression or unacceptable toxicity, 8 Gy single fraction on one metastatic lesion given day 8 from CTX start and IL-2, 500.000 UI twice a day i.v. day 1 to 5 every other week, starting the day after RT. We enrolled patients with end-stage for colon, breast, kidney and prostate cancer. Analysis was performed at baseline, the day after RT, after 28 days from treatment start and at disease progression. Assay focused on Tregs, CD8+, NK, MDSC, CD3-PD1, IL-2, IL-4, IL-5, IL- 6, IL-10, IL-12, IL-13, IL-17a, TNFα, IFNγ, TGFβ. We report baseline and post-RT data separately in patients with colon cancer (CC) and other patients (non-CC). Results: We report data from 8 pts with left colon, 6 with breast, 2 with kidney and 3 with prostate cancer. At baseline, cytokine expression was similar in CC and non-CC except IFNγ and IL-13, both less represented in CC. After RT, TNFα increased in both groups, but more evidently in CC. A clear increase in IL-10 and IFNγ occurred only in non-CC, while IL-2 increased only in CC. Cumulatively, CC and non-CC reacted differently to RT in terms of positive or negative changes of the analyzed cytokines. On the contrary, we did not observe clear differences in immune cells between CC and non-CC neither at baseline nor after RT. Discussion: The limited number of patients reduced the interpretation of the study. The differences observed are numerical, but not statistically significant. Colon cancer shows some peculiarities, including the low IL-13 and IFNγ value and a different response to RT. Further analyses investigations are in progress. Citation Format: Cristiana Lo Nigro, Dario Sangiolo, Vincenzo Ricci, Ornella Garrone, Andrea Abbona, Antonella Falletta, Anna Merlotti, Chiara Varamo, Massimo Aglietta, Loretta Gammaitoni, Oscar Bertetto, Marco Merlano. The immune landscape in colon cancer and its changes after radiotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 533.