I'm 59 years old - had stage 1b ER+/HER2- breast cancer but found after surgery to have two lymph nodes with cancer and a much larger tumor (7cm) so considered high risk. I've been on Verzenio and Anastrozole for the past 18 months. For both I had some false starts. I first started Anastrozole which gave me hives on my legs. It was weird. I stopped for a couple of weeks and restarted and no hives. With Verzenio, my liver enzymes shot up. Again, I stopped for a month, restarted, and no liver problems. I still have probably 4-5 placed on my regular blood tests that are "abnormal" each time (eg. low red blood cell; large blood cells) but these are normal, abnormal things that my oncologist isn't worried about, doesn't really affect how I feel, and will go away when I'm off the drug. But - diarrhea - ugh. I still have diarrhea a year and a half in. But over time, Imodium has become my best friend and I've learned how to predict when the diarrhea will come . . . mostly. It's a juggle between diarrhea and constipation from Imodium. I haven't had to change my life too much due to diarrhea - just pay attention more (eg. know where the public bathrooms are going to be when I go out). It was helpful to tell a handful of close co-workers with whom I have regular meetings about this side effect as I've had to duck out of zoom meetings a couple of times. They are very understanding. When I had a trip scheduled to fly to California for my daughter's graduation, my oncologist let me stop taking the Verzenio for 5 days which was great (happy gut!) When considering whether to take it, I asked myself if I could handle 24 months of this strong drug with side effects in order to have the extra protection against recurrence and I said yes. For me, I figured I could do anything with a stop date of 24 months. Sooooooooo - six more months and I'm done!
I trust my oncologist but also ask her in depth questions and have her provide the data on treatments (which she's happy to do). I want to be an informed consumer of healthcare, but also know that my oncologist is the expert who not only went to med school for this and had a fellowship at Fred Hutch Cancer Center, she's seen patients with cancer every-single-day for decades. I go in for labs and to see her every 6 weeks (which I think we be more spread out after I've done my 2 years on Verzenio). So if anything weird is happening with my health, she knows it.
I'd say if your oncologist is suggesting it, you can give it a try and see what side effects pop up. You can always stop, take a break or pause & restart like I did.
Also - here's a short, not super scientific video that helped me understand how the drug works: https://www.youtube.com/watch