Anyone taking cyclin-dependent kinase (CDK) 4/6 inhibitors?

Using brand names for ease. I’ve been taking Kisqali 400 mg for 4 years for recurrent breast cancer IDC ER/PR+ HER2- BRCA2+ CHEK2+ Ki-67 50%. Had a double mastectomy the first time around, stage 1 but genetic mutations. 7 years later recurrent BC in chest wall. Removed tumor, positive margin. 37 radiation treatments then started Kisqali and Letrozole at the same time. Can’t do chemo because of pre-x neuropathy. Because the BC is so aggressive my oncologist felt some cells likely got away before surgery. Once the tumor was removed, nothing large enough to show on CT scan. 4 years later still nothing showing except the non-related lung NETs neuroendocrine cancer — 50+ slow growing tumors.

Originally took 600 mg Kisqali but immediately had the dangerous heart rhythm QT prolongation. Lowered dose to 400 and it stopped. I have had paroxysmal afib since 5 days after starting Kisqali. My worst side effect. Ongoing issue. First year or two extreme fatigue and trouble staying awake. The fatigue is less severe now than the first two years. I still run out of energy quickly. I now have serious insomnia issues rather than sleepiness but that could be the Letrozole. Hair thinning. Lower BP. Aggravates my neuropathy. Some joint pain probably from Letrozole. It lowers immunity. I wash my hands a lot and avoid sick people but am not overly concerned about lower immunity. When I catch a bug, I’m sicker and for longer than in the past. It sounds awful when I list it out but I will stay with the treatment as long as it’s effective. I still enjoy life and am still here.

Everyone reacts so differently to meds. One person has severe side effects and another has none and everything in between. I’m typically prone to adverse side effects with most meds.

Why Kisqali? My oncologist chose that over Ibrance and Verzenio because the clinical trials showed all 3 meds extended progression free survival time but only Kisqali showed an increase in overall survival. Ask your oncologist to show you the latest clinical data for each.

I do not like the heart rhythm issues from Kisqali but want the most effective med. Verzenio commonly causes severe diarrhea and that’s a quality of life dealbreaker for me. Just my preference. I would love to take a break from meds but don’t want to risk it. Lastly, I started octreotide for my lung NETs 2 months after the Kisqali and that compounded the original side effects. Hard to know how much fatigue and hair thinning (not bald) each med is causing.

Hope this helps. Prayers for your decisions and successful outcome.

Jan 2022, age 72, Stage 4 BC spread to a few bones and C3 vertebrae. 5 sessions radiation took care of the bones. Then I took Ribociclib 600 for 19 days and nearly collapsed in a train station due to neutropenia. 2-3 weeks later tried 400. After 9 days sharp pain in head so I quit it but not soon enough. My liver enzymes AST and ALT shot up near 1200. I was hospitalized for 10 days for 24/7 infusions. The only drug that brought the numbers down was a steroid which left me with side effects I’m still dealing with today. I deeply regret taking the Ribociclib. I took letrole from Feb - June 2022. Now I’m supposed to take it everyday but I don’t want the effects of not enough estrogen to brain and bones etc. Eventually I learned about the Metabolic Therapy for cancer which makes more sense to me. So I’m focused on that.
These are hard decisions and all the oncologists are not on the same page when they discuss these dangerous drugs.

Thank you for sharing and I am so sorry for your experience. Can you say what type of BC you were diagnosed with?

Thank you for your reply. This was helpful to me because it shows efficacy of this drug for ILC. Your cancer was first diagnosed in 2016 and you just had a mastectomy 3 weeks ago. You did not have any surgery for 8 years, only drug therapy? Is this correct?

In 2016 I was diagnosed with invasive ductal carcinoma. I had a lumpectomy and a thirty- day radiation. Based on my Mamaprint result chemotherapy was not needed. Took Tamoxifen for 8 years. But last April I was diagnosed with ILC after a core needle biopsy and a histopath on the same breast but located on a different quadrant. My oncologist recommended for me to take Ribociclib coupled with Letrozole instead of the regular chemo infusion but with mastectomy. She explained that the medicines have been very effective with her other patients with the same type of cancer- ER PR positive and HER2 negative- as I have.

I was diagnosed with ILC, HR+/HEr2 low MBC, metastasis to bones, no mutations. My first line was Verzenio + anstrozole. I was on it for 18 months when I had further progression to bones. Verzenio did cause some diarrhea but nothing terrible. I didn't need to use anti-diarrhea meds except maybe a couple of times. Overall it wasn't too bad in terms of side effects. Anastrozole caused neuropathy in my fingers. I had received steroid shots to 2 of my fingers for trigger finger. They are still a bit stiff in the mornings but it gets fine as I move them.
After progression onco put me on Kisqali + Faslodex. Almost no side effects from Kisqali, except low WBCs. However, I think it never worked for me. My CA tumor markers started to increase a few months after I started Kisqali and kept rising. I was being followed up with CT and bone scans and twice they came back stable. My onco ignored the rising markers and after I pushed for a brain MRI it turned out there are 2 spots in the brain.

I was diagnosed with ILC, HR+/HEr2 low MBC, metastasis to bones, no mutations. My first line was Verzenio + anstrozole. I was on it for 18 months when I had further progression to bones. Verzenio did cause some diarrhea but nothing terrible. I didn't need to use anti-diarrhea meds except maybe a couple of times. Overall it wasn't too bad in terms of side effects. Anastrozole caused neuropathy in my fingers. I had received steroid shots to 2 of my fingers for trigger finger. They are still a bit stiff in the mornings but it gets fine as I move them.
After progression onco put me on Kisqali + Faslodex. Almost no side effects from Kisqali, except low WBCs. However, I think it never worked for me. My CA tumor markers started to increase a few months after I started Kisqali and kept rising. I was being followed up with CT and bone scans and twice they came back stable. My onco ignored the rising markers and after I pushed for a brain MRI it turned out there are 2 spots in the brain.

I am so sorry for what you are going through. Did Verzenio + anastrozole stopping the progression for 18 months? How was that track?