After treatment (surgery, radiotherapy, chemotherapy), you can relax after driving away the sinful oral cancer; however, you need to keep yourself under constant observation and seek regular review by your doctor. One of the core purposes of doing so is to hope for early diagnosis and treatment of re-occurring oral cancer. Reoccurring oral cancer can be either recurrent cancer or second primary cancer. How to “prevent” the recurrence of oral cancer? The most concerned question of patients after oral cancer treatment is: how to “prevent” oral cancer from recurring? The answer to this question is: it cannot be “prevented”. The reason is that after surgery and postoperative adjuvant radiotherapy, the determining factor of whether oral cancer recurs or not is whether there is still cancerous tissue in the body. If there is still cancerous tissue in the body, it will develop into a cancerous lesion at some time in the future (usually up to three years after treatment for squamous cell carcinoma), which is called recurrent cancer. Recurrent cancer can be sensed, seen, touched, or detected with the help of modern medical imaging techniques (e.g., CT, MRI). Why is there still cancerous tissue remaining after treatment? Some people ask why there are still cancerous tissues after surgical resection, and in some cases with postoperative radiotherapy and chemotherapy. The reason is that the surgeon can only see cancer cells that have accumulated in large piles, and these are superficial “piles” of cancer cells. The “small piles” composed of dozens or hundreds of cancer cells, or the “big piles” drilled into the deeper parts of the cancer cells cannot be seen, touched, or detected by any instrument at all. Let’s make an analogy: a person standing on the upper floor can only see the ants on the surface of the ground, but not the ants that have left the ants, not to mention the ants that have drilled into the ground. The ants have entered the sewers, which is equivalent to lymphatic metastasis; the ants are flying and drifting with the wind, which is equivalent to distant metastasis. Since it is impossible to prevent oral cancer recurrence, what should be done? There is a large portion of recurrent cancer foci of oral cancer, if they are found early enough and the cancer foci are small, the treatment is simpler and the hope of complete cure is higher. Therefore, after oral cancer treatment, it is impossible to “prevent” oral cancer recurrence, and one can only hope for early diagnosis and early treatment in order to achieve the final victory in the fight against cancer. It is not recommended to adopt Chinese medicine, “enhancement of immunity” and other ineffective measures or measures that have not been proved to be effective by modern medicine. These methods cannot kill the remaining cancerous tissues in the body, nor can they “prevent” recurrence. How to diagnose and treat recurrent oral cancer early? Patients should familiarize themselves with the oral cavity after surgery and radiotherapy, and know whether there are any changes in the oral cavity after treatment; they should keep in mind that oral cancer may recur. Follow the surgeon’s instructions and have regular checkups; if there are any changes, consult the doctor promptly. Most squamous cell carcinomas of the oral cavity that are found to recur are found six months to three years after treatment; be more vigilant during this period of time. In the case of malignant tumors of salivary gland origin, there is a delay in detecting recurrent cancer. Can blood tests detect recurrent oral cancer? No, it cannot. To date, scientists have not found a reliable blood test that indicates recurrence of oral cancer. Since it is not possible to “prevent” the recurrence of oral cancer, is it possible to resume smoking, drinking and chewing betel nut? Smoking, drinking and chewing betel nut are prohibited after oral cancer treatment. This is because some patients may have multiple primary cancers. Multiple primary cancers are not “related” to the previously treated oral cancer, but other parts of the mouth that were normal during the previous treatment for oral cancer have become cancerous and become a new oral cancer. The exact cause of oral cancer is unknown, but smoking, drinking and betel quid chewing are the risk factors. Therefore, there are often patients who feel wronged, “Why do so many people smoke, drink and chew betel nut without getting oral cancer?” It is true that there are many people who are involved in these bad habits, and they belong to the “lucky ones who are fine”. However, it is certain that oral cancer survivors do not belong to this kind of “lucky ones”. Their oral mucosa is easy to become cancerous when encountering risk factors such as smoking, drinking, betel nut, etc. Even if the first cancer has been cured, the risk of cancerous changes in other parts of the body is greater than that of other people. Therefore, it is necessary to stop smoking, drinking and chewing betel nut decisively.