You are having a recurrent tumor and you have been operated 4 times in the past. According to your description you have a recurrence again within the oral cavity which is uncomfortable for you. Let me be very categorical in stating that you stand very little chance of cure at this stage, the only thing that can be done at this stage is palliative treatment to give you a good quality of life. Since you had a single course of radiotherapy for your primary tumor in the post operative setting, I would suggest you consult a radiation oncologist for considering a re-irradiation along with some concurrent chemotherapy if your general condition permits so. Now a days many improved techniques of radiation therapy are available which cause minimal side effects and these were not available 20 years back when you received your radiation. Moreover this radiation can be combined with many new chemotherapy drugs and improved chemotherapy regimes. Meet a radiation oncologist first and let him decide on the future course to give you a good QOL (Quality of Life).