What is the most important factor that causes cancer? Genes? Pollution? Diet? Smoking? None of them, the most relevant factor to cancer rates is age! In 2013, China published for the first time its Annual Report on Tumors, which showed, firstly, that the incidence of cancer increases exponentially from the age of 40 onwards for both men and women; and secondly, that older men are more likely to get cancer than women, mainly prostate cancer. The vast majority of cancers we are familiar with: lung cancer, liver cancer, stomach cancer, rectal cancer, etc. are diseases of the elderly! As the average life expectancy increases, it is inevitable that the probability of getting cancer will increase. Why do flies rarely get cancer? Because they have a short life expectancy and die before they get cancer. The reason our pet dogs and cats get cancer is that their life expectancy can be upwards of 10 years, which is equivalent to 70-100 years for a human being, so the probability of getting cancer is not low. So do other factors matter? Definitely. Cancer occurs due to genetic mutations. There are more than 20,000 genes in our body, and about 100 of them are directly related to cancer. If one or several of these cancer genes are mutated, the probability of cancer is very high. Why and when do genes mutate? Mutations occur during cell division, and every time a cell divides, a mutation occurs, but most of the mutations are not in the key genes, so cancer is still a small probability event. When do cells divide? When growing or repairing tissue.