system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do children get leukemia more frequently than other types of cancers?
gpt
Most cancers are due in part to some external source, such as radiation (including from the sun) or carcinogenic compounds. Exposure to these carcinogens has a chance of producing mutated cells which are cancerous. Since exposure to some extent is unavoidable, it's simple mathematics that the longer you live, the more often you are exposed and the more likely you are to develop a form of cancer. Additionally, many cancers take some time before they develop into a medical problem. For the most part, it is unlikely that a child has lived long enough to develop cancer.

Leukemia is a cancer that is particularly influenced by hereditary factors, and is also fast-acting compared to certain other cancers. Hence it is both more likely to begin at a young age and to develop into a medical problem (which leads to diagnosis) while the person is still young, compared to other cancers.

But leukemia does not uniquely affect children; most cases of leukemia are in adults. It is just that children are comparatively less likely to have other cancers.