In general, eating leftovers from a cancer patient is not contagious. Cancer is a disease of genetic abnormality triggered by a combination of factors over a long period of time. When the body is affected by chemical, physical, viral and other carcinogenic substances in the environment, and/or due to its own genetic, endocrine, gender, age and other factors, a series of genetic abnormalities can occur, resulting in the formation of cancer. Cancer is not a contagious disease, and its cancer cells, although spreading in the body of a cancer patient, are not contagious through diet, so eating leftover rice from a cancer patient is not contagious. Although cancer is not contagious, some factors that induce cancer are potentially contagious. For example, some stomach cancer patients with Helicobacter pylori infection may also be infected with Helicobacter pylori as a result of eating together. Patients who suffer from hepatitis B and eventually develop liver cancer may be infected with hepatitis B if they share meals and drinks with them. To summarize, eating leftovers from cancer patients does not lead to cancer infection, but it is not recommended.