Abstract 275P
Background
The development and prognosis of colorectal cancer (CRC) is affected by the antitumoral immunity of the tumor’s microenvironment. Patients with high expression of CD3+ and CD8+ T-lymphocytes in the tumor epithelium and stroma have a better prognosis. The prognostic role of antigen precenting cells (APCs), such as dendritic cells and macrophages, has been less extensively established. These cells can activate the CD8+ T-cells through tumoral antigen presentation, linking the innate immunity to the adaptive antitumoral immunity. Previous studies among CRC patients have suggested that patients with lower expression of CD11c, a marker for APCs, may have poorer survival. In this study, we evaluate the effect of CD11c expression on the disease-specific survival (DSS) among colon cancer and rectal cancer patients separately.
Methods
Using immunohistochemistry, the expression of CD11c on tissue microarray samples was evaluated for 516 patients treated surgically in the Helsinki University Hospital between 2000 and 2005. The samples were categorized as low expression with <5% positive stromal area, and as high with >5%. Colon and rectal cancer patients were analyzed separately, using Cox-regression for survival analysis.
Results
Lower expression of CD11c indicated better DSS among rectal cancer patients (p<0.001) and right-sided colon cancer patients (p=0.03), but not among left-sided colon cancer patients (p=0.41, log-rank test). The differences in DSS between low and high CD11c groups were significant among rectal cancer patients who did not receive preoperative radiation therapy (RT, p<0.001), but remained non-significant among rectal cancer patients treated with preoperative RT. In multivariable analysis, after adjustments to age, sex, stage, grade, and MMR-status, lower CD11c expression remained as an independent prognostic factor among rectal cancer patients (p=0.009), but not among colon cancer patients (p=0.15, Cox-regression).
Conclusions
We demonstrate that CD11c has a potential as a prognostic marker for rectal cancer patients, but not necessary for colon cancer patients. A deeper understanding of immunological mechanisms that potentially differentiate colon and rectal cancers could enhance their treatment strategies.
Legal entity responsible for the study
Research Group of Caj Haglund.
Funding
Finska läkaresällskapet, Medicinska understödsföreningen Liv och Hälsa, Sigrid Jusélius Foundation.
Disclosure
All authors have declared no conflicts of interest.