The German Cancer Institute, on the basis of long-term (in my opinion, 20 years) observations, has established that meat - primarily beef, to a lesser extent - pork and to a slightly lesser extent - lamb - is a carcinogenic product, and in this regard - a direct cause of cancers of the rectum and some other internal organs. One of the risk groups is workers in slaughterhouses and butcher shops. When you enter such shops, try to be there as short as possible! The highest rates of cancer in the digestive organs are in the USA, Australia, Latin America, and Europe. The lowest disease rates are in Japan and South Korea, although there in recent years the disease curve has crept up due to a change in diet in favor of meat. Milk, as well as other dairy products, is carcinogenic.
In addition, the cause (of course, not in all and not always) cancer is various, at first glance, "innocent" diseases, incl. infectious and viral - gastritis, pancreatitis, cholecystitis, food poisoning, etc., as they create a favorable background for cell mutations.
Correlation is not causal. Yes, according to statistics, vegetarians are less susceptible to cancer, but this is not due to the lack of meat in the diet, but due to the fact that vegetarians pay more attention to their health, they do not have bad habits and all that. The meat itself, if it is of more or less quality, cannot cause cancer. The carcinogens are not that strong there.
A person who does not eat meat is called an android. And he is more likely to break than get sick.
If we are talking about vegetarians, then the chances are reduced, but in a very distant sign. And if you compare it with a group that eat boiled meat, then even less.
This myth came from the book "Chinese study", I recommend that you read this video youtu.be if you are interested in understanding why this is a myth.