The relationship between the adaptive CD4 þ T-cell response and human cancer is unclear. The oncofetal antigen 5T4 is expressed in many human carcinomas, including colorectal cancer cells, but has limited expression on normal tissues. We previously identified anti-5T4 CD4 þ T cells in a proportion of patients with colorectal cancer, and we extended this study to examine whether the quality or quantity of the T-cell response reflects tumor stage. An overlapping peptide library spanning 5T4 was used as a target to enumerate cognate IFN-g cells [measured as spot-forming cells (SFC)/10 5 cultured T cells] in peripheral blood-derived lympho-cytes following a 14-day in vitro culture period comparing patients preoperatively (n ¼ 27) to healthy controls (n ¼ 17). Robust 5T4-specific T-cell responses were present in 100% of healthy donors. There was a steady loss of T-cell responses with advancing tumors with a significant negative correlation from stage I to III (P ¼ 0.008). The predictability of the decline meant <200 SFC/10 5 were only found in subjects with stage III colorectal cancer.

Current dogma suggests that tumor-reactive IFN-γ–producing (TH1-type) T-cells are beneficial to patient outcome; however, the clinical consequence of these responses with respect to long-term prognosis in colorectal cancer (CRC) is not understood. Here, we compared the utility of preoperative, peripheral blood–derived IFN-γ+ T-cell responses specific to carcinoembryonic antigen (CEA), 5T4, or control antigens (n = 64) with tumor staging and clinical details (n = 87) in predicting five-year outcome of CRC patients who underwent resection with curative intent. Although disease recurrence was more likely in patients with stage III tumors, the presence of preoperative, CEA-specific IFN-γ–producing T-cells identified patients at a statistically significantly greater risk of tumor recurrence following surgical resection, irrespective of tumor stage (odds ratio = 5.00, 95% confidence interval = 1.96 to 12.77, two-sided P <.001). Responses to other antigens, including 5T4, did not reflect outcome. Whilst these results initially appear surprising, they could improve prognostication and help redirect adjuvant treatments.