Calling all dermatologists! Fluorouracil application question

I recently went to a new doctor for a consultation preliminary to a physical exam (my first since 2020. Also my first since relocating to Oregon). One of the things he immediately noted is that I have a few actinic keratoses on both of my hands and forearms. Given my family history of melanoma (it killed my mother in 2009), he felt it merited attention, and wrote a referral.

Thus it was that I found myself in a dermatologist’s examining room a week ago. She took one of the larger lesions for analysis, and wrote me a prescription for Fluorouracil cream, to be applied BID for three weeks, after which I was to discontinue for a month, then resume the regimen until a follow-up in February. She also warned me to expect considerable discomfort as the drug worked to fight any pre-cancerous cells in the AKs, even to the point of prompting me to curse her name (which is probably why she wouldn’t reveal her true name to me. But I digress).

I picked up a 40-gram tube of the cream that afternoon, and began applying it in accordance with the instructions on the sheet the doctor gave me (a glob about the size of a chocolate chip on each forearm, which I then spread as far as I could across my arms and the backs of my hands). The instruction sheet mentioned applying it in a “thin film,” which in my mind, I interpret as NOT something that massages into the skin and leaves no visible trace. But I guess a white cream of this viscosity can’t really be expected to remain visible, so it could have just been a poor choice of terms.

Anyway, I’m mostly confused by the fact that I haven’t experienced any discomfort at all. This leads me to wonder if I’m using enough of the cream to achieve a therapeutic effect. But it’s only a 40-gram tube, and using it twice daily for three weeks only gives me about one gram per application. Using more than I currently am would almost certainly result in running out prematurely.

Another possibility is that I feel no discomfort because none of my keratoses are pre-cancerous, so my regimen is having no more effect than would putting on some Jergen’s hand lotion. Given the aforementioned family history, I don’t want to bank on that, but knowing whether it’s a plausible hypothesis* would be helpful.

*After all, putting salicylic acid on a non-wart still stings like the dickens; why should 5FU not irritate healthy skin (although to be sure, salicylic acid is applied with a glass rod and 5FU is applied with naked fingers)?

Anyway, TIA for any knowledge you can drop (I am waiting on a call back from the dermatologist).

I’ve used Fluorouracil cream three or four times. I don’t recall any major discomfort other than some fairly intense itching. It also looked pretty gross when the affected area started turning red and the skin started flaking off. Wash your hands well after applying the cream, you do not want to get it anywhere near your eyes.

Being pale, balding, aging and living in here makes skin cancers an occupational hazard.
Australia has one of the highest rates of skin cancer in the world.

I see a dermatologist every 6 months and he usually does some minor reparative/preventative work with his liquid nitrogen canister. Nothing malignant has yet been diagnosed

He wrote a script for Fluorouracil in Feb which I had filled but I have so far baulked at the notion of self-medicating chemotherapy. It’s recommended for use as a winter treatment so that won’t be done until next year, assuming I can screw my courage.

I also have actinic keratoses on my forearms, and have treated them three times with Fluorouracil cream over the past few years.

It takes a long time for it to work. My dermatologist said to apply it for a couple weeks, but each time I kept applying it until the tube was depleted (around 4 weeks). At $70/tube, I wanted my money’s worth!

Afterwards your arms won’t look “good as new.” There will be discoloration. But at least that’s better than cancer.

Before going to bed, I would apply the cream to my arms, and then wear a long-sleeve shirt to bed. I did this because I didn’t want the cream to transfer to the bed sheets.

Oh, and from here on out, your forearms should never see the Sun again. Always wear a long-sleeve shirt when you’re outdoors and when the Sun is out. During the summer I “double up”: I will wear long-sleeve shirts and sun sleeves under the shirt.

The Sun is not your friend. Shield yourself from it, and take a Vitamin D supplement everyday.

Thanks, all. I did receive a call back from the dermatologist’s office this afternoon. She said I might need a couple of weeks of treatments before the discomfort begins. She also said that the pathology report found squamous cell carcinoma cells in the biopsy, so I have to go in next month and have the rest of that lesion excised.

I’ve used topical fluorouracil a couple of times. As you may know, it’s a standard rather toxic chemotherapy agent which is administered internally for any number of nasty kinds of cancer. The skin cream is the same active ingredient, just in a pretty light dose.

As others have said, it takes awhile to have an effect. You’re more or less giving yourself a monster sunburn which will kill a lot of your skin, including the cancerous stuff. Once the skin gets all red and itchy and uncomfortable, then you’ll keep using the cream for a while longer per their instructions. That’s when the process gets uncomfortable.

Living here in FL with light English/German skin, my doc generally freezes the obvious free-standing AKs when I see him every quarter. And biopsies a couple of spots that usually turn out the be BCC or rarely SCC. I’m awaiting 3 of those results right now. If the AKs are bustin’ out all over, then it’s time for the fluorouracil.

FYI there’s a variant treatment out now that’s perhaps worth checking with your dermo about …

I have done the 5-FU (as they call it) cream for 30 days and been a ruddy peely mess taking a further month to heal back to normal. The last time I needed that treatment he prescribed something different.

Use the same 5-FU cream 2x/day, but only for a week. And at the same time apply a different cream agent, calcipotriene, also 2x/day for the same week. In his explanation, research shows the sum of the two produces the same clinical results in much less time with much less collateral damage. When I did the treatment that way I had little peeling, light discomfort, and was back to work in 10 days, not 60. I’ll be doing that here in January again.

I’m sure not trying to practice unlicensed medicine on you via internet, but it might be something to ask your experts about.

Or better yet, use a wooden stick (for instance, a tongue depressor) to apply the cream, although if it needs to be applied to fingers, then it can be done that way. Make sure any objects that contact the cream, and that includes your treated skin areas, are not accessible by pets or small children.

Your doctor was right, it doesn’t work right away, but when it does, you WILL see it.

I’ve used it on three different occasions. I did have pain, but not until the second week. Expect to get red swollen areas, especially where there are active actinic keratoses.

Remember, this medication interferes with cell division by shutting down the production of RNA, which cells need to grow and multiply… As precancerous/cancerous cells are dividing much more quickly than normal, those targeted cells will respond more quickly. And of course don’t use it any longer than the directions indicate. Best of luck - my treatments were very successful.

If one is not wearing medical gloves while applying this stuff by hand, they’re getting a big dose where it doesn’t belong. Unless of course the hands are part of the planned treatment area.