Purpose: The primary goal of this study was to assess the effectiveness of interferon gamma (IFN-gamma) to prevent tumor relapse following potentially curative surgery in patients with high-risk colon cancer. A secondary goal was to determine the effect of IFN-gamma on immune function and to correlate alterations in immune parameters with survival.
Patients and methods: Three to 4 weeks after undergoing resection of all known malignant disease, 99 patients with stage II, III, or IV colon cancer were randomly assigned to receive IFN-gamma 0.2 mg total dose by subcutaneous injection daily for 6 months or observation. Serial assessment of human leukocyte antigen (HLA)-DR expression and Fc receptors on peripheral-blood monocytes was conducted in 24 patients who received IFN-gamma and 27 control patients.
Results: With a median follow-up duration of 59 months in patients still alive, there was evidence of a detrimental effect on time to relapse (P = .03) among patients who received IFN-gamma. There was no significant difference in patient survival (P = .12). This study has sufficient power to rule out a 25% reduction in death rate for patients who received IFN-gamma (P < .05). Significant enhancement of immune function was observed in patients treated with IFN-gamma as measured by HLA-DR expression (P < .01) and Fc receptors (P < .001) on peripheral-blood monocytes.
Conclusion: This study effectively rules out any clinically meaningful benefit for IFN-gamma as surgical adjuvant treatment for patients with high-risk colon cancer. Although significant enhancement of nonspecific immune function was seen with this dosage administration schedule of IFN-gamma, this was not associated with any demonstrable antitumor effect.