One of the hallmarks of oral cancer is its inherent insensitivity to Radiotherapy. We have analysed the tumor metabolites and quantization of biochemical and bioenergetic metabolites by NMR spectroscopic analysis. In this study, trace element selenium exhibit dual nature in oxic and hypoxic conditions as an antioxidant and anticarcinogen respectively, indexing its radiosensitising effect, denoting a remarkable decrease in tumor mass with the gradual disappearance of tumor characteristics and oxidative stress in oral cancer cases undergoing radiotherapy. Dual role of selenium as a radio sensitizer and radio-protector could warrant a significant progress in the cancer patients, as an adjuvant to the conventional therapies in oral cancer management. Key words: Selenium, Free radicals, Oral cancer, Radiosensitisation, Radiotherapy.