Yes, they, like most keratin outlets, are hammered by chemo and don’t seem to fully recover.
Like Debbie mentions, b vitamins, particularly biotin, are your best bet towards giving them a fair shot at growing with some integrity. I also think the over-all dried-up State we’re left in adds to the brittleness, particularly if your cuticles show evidence. Moisturize, moisturize, moisturize. I’ve found, of all things, using Lansinol cracked nipple cream for lactating Mother’s is an excellent cuticle and nail tx. I apply at bed time...and slap a little bit under my eyes for good measure.
Aside from that, the most immediate foil seems to be to keep a clear coat on at all times and don’t let it get chippy. Simply adds a layer of fake strength.
My fingernails and toenails were horrible during treatment. Lost both big toenails and it took forever for them to grow back - over a year. I'm a little over a year out of treatment of 8 months of chemo, surgery, 6 weeks of radiation and a year of hercepton. I had ridges, split nails and brittle nails forever. They always looked like I bit them down to nubs. I also had terrible peeling around them. I tried Hair, Skin & Nails and calcium but it didn't seem to help. One winter night I was putting Carmex (from a jar) on my lips (as I always do at bedtime) and decided to try it on my nails too. It has worked miracles. I rub it in every night and the peeling has stopped, my nails aren't brittle anymore, I do still have small ridges but they are getting better and my nails are actually growing. It's nice to give myself manicures again. I've been doing this consistently for about 4 months now.
I am three years out from chemo and my nails were doing well with a daily collagen supplement. Then six months ago "C" spread to by bones and I began to take Ibrace, the chemo pill. The cracking started back up. I've added biotin with no effect but recently began using Burt's Bees cuticle cream on my whole nails not just cuticles. I am showing some improvement.
For me keeping them short and painted really has helped with the peeling and sensitivity. Homestead Body butter and oils have really helped my dry hands and skin.