Fluorouracil - Can I use fluorouacil on my lips?

Judy, I would check with your doctor. Just know that if you do the treatment on your lips... there will be discomfort and temporary is a state of mind. It will not be a pleasant couple of weeks. Make sure you don't have any engagements planned for days 10 - 20. But if it prevents further cancer it may well be worth the effort. I suggest taking daily photos - it can make the process a little more bearable and later you can look back and say wow - that was a pretty miserable month.
Here's the response I see on US National Library of Medicine National Institutes of Health.
"Topical (5-fluorouracil [5-FU]) as a 5% solution was used to treat isolated actinic keratoses of the lips as well as diffuse actinic damage of the lower lip. Although producing considerable temporary discomfort(t) final results proved excellent, with recurrences in only two of 12 patients treated. Preliminary biopsy of suspicious infiltrated areas is mandatory, as is careful follow-up to ensure complete healing. Topical fluorouracil is an alternative to surgical excision of the vermillion border of the lip in those patients with severe diffuse actinic damage of the lips."