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Letrozole later onset side effects
I had chemo, surgery and radiation for HER2 stage 2 breast cancer. In March 2024 I was placed in anastrazole, and taken off it in May 2025 due to side effects which I now can’t completely remember. In July 2025 I was then placed on Letrozole and am still taking it. I have suffered from most of the side effects others mention including dry eyes, tendon issues in my wrist, exhaustion, mood changes, a very sore shoulder, etc. I was managing all of this ok, but last week I developed a severe pain in my lower back and it has not gone away. It hurts so much to stand up from sitting, bend over to tie my shoes, pet the dogs, etc. I would like to know if anyone else has experienced this as a late onset side effects others mention and if so, what did you do? I see my oncologist April 8 and would like to provide her with suggestions. Thank you!
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I’m interested in the occurrence of late side effects. I have seen in the literature that this does occur. I have been taking Anastrozole for two years and didn’t develop significant side effects until about three months after starting treatment. I had hoped my side effects had ‘ peaked’ but still struggled on with them. After eighteen months I suddenly began to develop quite severe hand symptoms, which I thought those who experience them usually get fairly early on in therapy. It seems that these drugs are ‘ the gift that keeps on giving’ and. I am just hoping no more ‘ surprises’ pop out of the cupboard!
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2 ReactionsNo but I have had back pain. A physical therapist helped me do exercises to strengthen my core and the back pain went away. I would get the pain checked. Could just be something else that can be addressed.
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1 ReactionBeen on Anastrazole and exemestane. Early on, for me at least, side effects were minimal but progressed the longer I was on the medication. Some were with both and one of those was lower back ache and stiffness in the hips to the point where when I stand up, I have to straighten, stretch and balance before I move. Luckily the back pain was not excessive but other pain was why I came off Anastrazole - that knife stabbing pain that moved around and could at times be incapacitating. After about 4 months on exemestane, the extreme fatigue settled in followed by insomnia at about 8 months coupled with weakness - can’t do what I used to do even a year ago. After 16 months, he just now put me on a medication vacation after which I will probably go on letrozole because 3-4 hours sleep isn’t cutting it. Now initially I did have mild osteopenia but declined bone meds (Prolia is nasty stuff and if you come off it wrong, can cause a cascade of spinal fractures) because didn’t feel needed at that level. Increased Ca, D3, K2, strength training and walking and after 2 years, bone scan was normal so currently no bone meds. But I guess those would be my questions - when was last bone scan, on or recently off any bone meds? Ask about checking for spinal lesions (x-ray, CT?) because of these drugs. Exemestane has less of an effect on bones than either Anastrazole or letrozole but as noted, other things are definitely there.
If you are taking calcium & D supplements a 24hr urine test can let your doctor know if your body is actually absorbing the vitamins/minerals you are taking. I didn't know that until I saw an endocrinologist. All the lab work I've had and she was the only one who had me do that test. Maybe sciatica? Back issues hurt!
Here is a reputable study looking at the symptoms you describe with AI's.....they describe it as a syndrome. I stopped AI's because of cardiovascular problems it gave me: super high blood pressure.
https://pmc.ncbi.nlm.nih.gov/articles/PMC8935546/