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Abstract
Objective: Previous studies have demonstrated the ability of non-lethal doses of radiation to alter the phenotype of tumor cells to facilitate immune mediated killing. This pilot study evaluated the tolerability of a vector-based vaccine targeting carcinoembryonic antigen (CEA) in combination with radiation therapy in patients with gastrointestinal malignancies metastatic to the liver.
Methods: Patients enrolled had progressive CEA+ tumors with metastatic liver lesions. Patients had received a median of three previous chemotherapy regimens, with a median of 2 months since their last chemotherapy regimen. Only 58% had metastatic disease limited to the liver. Vaccination commenced day 1 with biweekly boosters and split-course radiation (total 32 Gy) starting on day 21. Blood was collected at baseline and day 91 for immunological analysis.
Results/conclusion: A total of 12 patients were enrolled. There were no grade 3 or greater toxicities or grade 2 or greater hepatic toxicities. Median time on-study was 3 months, with the longest time on treatment being 5 months (n = 2). Immunological analysis was limited to two patients; neither showed an increase above baseline in CEA-specific T cells post-therapy. CEA/TRICOM vaccination in combination with low-dose radiation therapy is safe. There was limited evidence of activity in this patient population.
Acknowledgements
This study was supported by the Intramural Research Program of the Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland. The authors gratefully acknowledge the participation of patients and their families in this study, the assistance of the research fellows of the Medical Oncology Branch, NCI, and BL Casey for editorial assistance in the preparation of this manuscript.