Hi, Thanks for writing in. Cancer is a difficult condition and requires regular follow up. Tonsil cancer might have a good survival when compared to other cancers. If it has spread to your lungs then probably aggressive treatment is required and that is why they have suggested you for chemotherapy. Immunity is a concern but risk and benefit has to be considered when keeping in mind that your cancer is not completely under control. You might like to take precautions and then proceed with third round of chemotherapy for treatment. Please do not worry.