Stomach cancer patients may have indigestion with acid reflux, nausea and vomiting. Its possible that the stomach contents show bad breath through acid reflux, which may be sour and smells like stomach acid. In addition, bad breath is not always related to gastric cancer. For example, poor oral hygiene or other oral inflammation, as well as poor liver function and diabetes may cause bad breath, so it is also necessary to maintain oral hygiene, and it is recommended to go to dentistry to check whether there are any other problems. If the bad breath is caused by simple stomach cancer, on the one hand, you need to treat stomach cancer, and on the other hand, you need to maintain oral hygiene. Stomach cancer is a very common malignant tumor of digestive system, and if it can be treated surgically after diagnosis, it should be treated mainly by surgery, and after surgery, it can be treated with adjuvant chemotherapy and targeted drugs.