Abstract PO-031: Innate immune genes distinguish the immune microenvironment of early onset colorectal cancer

Despite a decrease in the incidence of colorectal cancer (CRC) over the last 40 years, the incidence of CRC in people under 50 years old is increasing around the globe. Early onset (≤50 years old) and late onset (≥65 years old) CRC appear to have differences in their clinicopathological and genetic features, but it is unclear if there are differences in the tumor microenvironment. We hypothesized that the immune microenvironment of early onset CRC is distinct from late onset CRC and promotes tumor progression. We used Nanostring immune profiling to analyze mRNA expression of immune genes in FFPE surgical specimens from patients with early (N=40) and late onset (N=39) CRC. We found three genes, SAA1, C7, and CFD, have increased expression in early onset colorectal cancer and distinct immune signatures based on the tumor location. After adjusting for clinicopathological features, increased expression of CFD and SAA1 were associated with worse progression free survival and increased expression of C7 was associated with worse overall survival. Our data demonstrate that the immune microenvironment in early onset CRC is unique, location dependent, and associated with worse outcomes. We propose that age specific immune signatures in the colorectal immune microenvironment can be used as biomarkers for prognosis as well as the development of targeted immune modulatory agents. Citation Format: Ivy H. Gardner, Ragavan Siddarthan, Katherine Watson, Elizabeth Dewey, Rebecca Ruhl, Xiangnan Guan, Zheng Xia, Liana V. Tsikitis, Sudarshan Anand. Innate immune genes distinguish the immune microenvironment of early onset colorectal cancer [abstract]. In: Proceedings of the AACR Virtual Special Conference on Tumor Heterogeneity: From Single Cells to Clinical Impact; 2020 Sep 17-18. Philadelphia (PA): AACR; Cancer Res 2020;80(21 Suppl):Abstract nr PO-031.