Post cancer treatment effects
Headaches and migraines are a known post treatment phenomena, which some doctors associate with the treatment and some don’t.
It is recommended to consult with a pediatric neurologist and always stay on alert to make sure these are only headaches
It could be a result from the chemo and other parts of the treatment or a combination of other biological processes (such as puberty, hormones, eyesight etc.).
and not something else which may develop over time under the headache ‘noise’.
A good book to learn, assess, and help treat migraines is “The Migraine Brain”.