Even the term “childhood cancer” is a problem, because it actually means cancers that strike infants, children, teens and young adults. That’s why the St. Baldrick’s Foundation often refers to “kids” with cancer.
While the word “kid” is slang and isn’t used in other countries, in the U.S., it is more inclusive. (At 21, you may be a college kid, but you’re certainly not a child!)
But the issue is far more serious than language. Adolescents and young adults with cancer are often treated as adults. If they received childhood cancer treatments instead, 30% more would survive!