I wish I had my eyebrows tattooed before treatment.! My eyebrows did not come back after chemo, but I always. had very thin, light eyebrows. Had them tattooed on a few months after treatment.
If you do, give yourself about a week for proper healing.
Heads up, way more painful than I thought, but so glad I did it.

I've had my eyeliner tattooed since 2007 and have many other tattoos, including a full sleeve and a partial sleeve. I stopped working on the 2nd sleeve after I was diagnosed with cancer the first time because I couldn't afford to spend the money on tattoos and at other times my immune system wasn't healthy enough to get new tattoos. Ask your oncologist first if your blood counts are healthy enough to get tattooed.

I know a couple of women that had their eyebrows done, but had issues with the color and type of ink that was used changing to an unnatural color for eyebrows. If you go this route do your homework and find a qualified and well experienced tattooist that specializes in makeup style tattoos. This is not the type of tattoo that you get from a regular tattoo shop.

As far as healing goes, the bulk of the healing on any tattoo is complete after about 2 weeks, but the new skin that grows during that time is still fragile. It takes 4 to 6 weeks after any tattoo for the new skin to grow in and toughen up and get back to normal. You will also want to moisturize your skin regularly the first few weeks, especially until new skin has formed. You don't want your new skin to dry out enough for scabs to develop because scabbing can result in some of the tattoo ink being pulled out of your skin and leave you with blank spots that need to be touched up later on.