I read that those with a high baseline wbc are more at risk of various cancers- true? mine is always 8.5-10, high end normal range and differential.

Possibly true.: There have been a few studies, mostly in older patients, which have shown an increase of certain cancers in patients who maintain a high white blood count. This is not a definitive finding, and the reason is unknown. It may mean that there is a link between chronic inflammation, which may affect the white blood count, and cancer formation. There will certainly be more studies in the future.