Purpose: Tumor necrosis factor-alpha enhances x-ray killing of human tumor cells in vitro and enhances tumor control when combined with radiation in animal tumor models. To determine the toxicity and maximal tolerated dose of tumor necrosis factor-alpha given daily during radiotherapy, we conducted a phase I dose-escalation study combining tumor necrosis factor-alpha and radiation.
Patients and methods: Thirty-one patients, including 14 patients with locally advanced primary tumors and 17 patients with metastatic sites, were entered into this study. Recombinant human tumor necrosis factor-alpha was administered intravenously at doses ranging from 10 microg/m2 to 150 microg/m2 4 hours prior to each radiation therapy session, which was given on consecutive days for a minimum of 2 weeks. Radiation was prescribed to localized fields, with dose fractions ranging from 150 to 300 cGy/day for palliation or control of locally advanced tumors.
Results: Major toxicity requiring withdrawal from the study was independent of tumor necrosis factor-alpha dose and occurred in seven patients. Symptoms included angina in two patients, and hypotension, respiratory distress, atrial fibrillation, allergic reaction, and progressive leukopenia in one patient each. A tumor necrosis factor-alpha dose of 150 microg/m2 was the maximum dose administered. No single dose-limiting toxicity was observed and a maximal tolerated dose could not be defined. There was no obvious increase in in-field toxicity. Response to treatment was assessed in 20 patients. Complete regression within the irradiated field was achieved in four patients, partial regression in four, and a minimal response in four. A trend toward a greater response rate at higher doses of tumor necrosis factor-alpha was observed.
Conclusions: The maximal tolerated dose of tumor necrosis factor-alpha when given with radiotherapy is at least 150 microg/m2 and a dose-limiting toxicity was not observed. Future studies will show whether responses to treatment are increased over those expected with radiation alone. Tumor localization of tumor necrosis factor-alpha by gene therapy combined with radiation therapy may eliminate the systemic toxicity we observed.