...This is such a great question.
I do know patients who have used fluorouracil on their scalps. Some have opted to shave their heads in order to do the treatment. If you are interested in talking with some of them, I would like to suggest a Facebook support group for users of fluorouracil. It's a wonderful source of advice and tips.
Here is the link to join:
https://www.facebook.com/groups/191070307590515
Our site doesn't have a lot of scalp-specific articles when it comes to this cream. I did a little digging and found this information on the results on the scalp. It doesn't give any tips for using it on the scalp; it just mentions that it is most effective on the face and scalp. That is encouraging.
https://www.aafp.org/afp/2010/0515/p1186.html
I know that applying the cream to the scalp beneath the hair is a challenge but not impossible. It is worth talking with your doctor to see what his/her recommendations are and see if they can offer you any tips from other patients.
I wish you all the best as you move forward. Please keep us posted on your progress! We are here for you!
April, SkinCancer.net, Moderator