Afinitor +ESR1 mutation for the hive mind.

[Pbsoup]

Hi

I am starting Afinitor on Wednesday after a mixed scan a few weeks ago after 6 months on Orserdu. It suddenly dawned on me that Afinitor is combined with estrogen therapy, likely an AI. But doesn't the ESR1 mutation cause AI resistance? In which case does that make Afinitor less effective?

I will of course ask my doctor but that won't be for a week or so. In the meantime I thought that someone here might have had the same question and had it answered...or is doing well on Afinitor despite the mutation... or is otherwise clued in on this.

Thanks as always! P

[Eliactida1955]

Sorry it did not work for me at all but might for you. After use I had a pacemaker insertion and dr thought it was Infinitor. Try it and see and I wish you the best.

[Pbsoup in reply to Eliactida1955]

Yikes. I hope that went OK. I know heart issues can be a side effect.

[Eliactida1955 in reply to Pbsoup]

Try it -wish you the best. We are alive!!!!

[awesome4ever]

Hi P. For what it's worth Afinitor is usually taken by itself as an effective cancer treatment for many cancers. It is only with ER PR + breast cancers that they add the AI. Where I live genomic testing is not routinely done so I don't know if I have developed the ESR1 mutation or not. I am on Afinitor and Exemestane and have had 2 separate 3 months apart scans that show stable so it is working for me.

Do you know if you have the ESR1 mutation or are you just thinking ahead? Regardless rest assured Afinitor works well on its own too, but if your cancer is still generated by estrogen then likely it would be best to add an AI. Good luck.

[Pbsoup in reply to awesome4ever]

Thank you. That’s interesting and very helpful. I’m sure my oncologist knows what he’s doing too. I just want this to work for a bit while I explore trials and wait for other things to come out.

[atoth17]

Hello P,

I was on Afinitor (Everolimus) and Fulvestrant for a few months recently (August-October). I can’t really speak to knowing how it works with an ESR1 mutation but it was a tolerable drug and since it comes in pill form, it gave me a nice break from the infusion chair. Unfortunately, I had progression in my liver so I am back to IV chemo.

Good luck,

Allison

[NPmary]

The ESR1 mutation develops in conjunction with AI resistance/treatment failure. If you live in the states Orserdu is FDA approved only if you have the ESR1 mutation (so I'm assuming you were tested and have the mutation. My understanding is that in that case you wouldn't be a candidate for an AI. Good luck, let us know how you are and what you learn. 🌺

[Pbsoup in reply to NPmary]

That's what I thought too. My MO has put me on Afinitor with Letrozole. I start tomorrow and will see him next week so will ask for his rationale.

[NPmary]

You might want to consider a second opinion. You should also call the company that did your lab testing for the mutation, get a copy of your report. Mine was available the h ollowing week, it clearly states that I have the mutation and should not take lettozole they named another drug not to take I think it was another AI ' I can look it up if you want me too ig the c ompany that did your testing was Guardant ' let me know and I will give you their phone number that you can call for your report. If I were you I would definitely get a second opinion and if you do have the mutation I would absolutely switch doctors. I had to do this myself for different reasons - my only regret was not switching docs sooner. You can do this. Please know that you deserve quality care, respect, and compassion. Let us know how you're doing and how things work out. Mary 🌺

[Pbsoup in reply to NPmary]

Thanks. I’ll ask him next week. He knows I have the mutation because I was just on Orserdu. Apparently Tamoxifen works ok with the mutation too—and can be paired with Afinitor so will ask about that

I just wonder if he feels the Afinitor does the heavy lifting in this case. Also I can always swap estrogen treatment. I’ll only be on it a week when I see him.

And may consider a second opinion.

The backstory is he wanted me to try enhertu but I worried about side effects. I asked about Afinitor as a last try at an oral treatment and he agreed, partly to humor me I think. I also want to explore trials. There are some interesting ones for HR 2 low on the horizon. ..

[NPmary in reply to Pbsoup]

Good luck, let us know how it goes.

[awesome4ever in reply to Pbsoup]

Hi P. I will be eager to see what you post next week as well. My thoughts from my research is that in breast cancer Afinitor is marketed to be used in combination with an AI and often that determines how oncologists can order. Also since you were identified as having the ESR1 mutation but despite that didn't respond well to Orserdu , perhaps it was because the VAF% was low. Physicians often just look for the mutation to be identified and then they order the drug. Realistically the likelihood of the drug being effective is low if VAF% is low.

So going forward there is no risk of you taking an AI knowing you have the ESR1 mutation. There is also a way to see if you have a low VAF% to the mutation can perhaps the cells start reacting to the AI therapy again. All things are being studied and results will be a long way off from being reported.

If I remember correctly you go to a large cancer center in California so I'm sure your oncologist is on top of things. Anyway good luck with your new treatment line. Take care.

[muzzatron in reply to awesome4ever]

Hi as we know drugs dont have a perfect response, luck of the draw. Fulvestrant is the next line of therapy after AI resistance here (oz) as some efficacy with ESR1. Could you expand on VFA%.

[Hopeful4Cure in reply to muzzatron]

I too would be pleased to understand vfa% as muzzatron has asked as well and surely many others. Long timers assume, we all know acronyms and heavy medical language, when we don't. Instead of emphasizing on terminology, many of us are left asking question's, which are never answered.

[muzzatron in reply to Pbsoup]

You might want to check that Tamoxifen does not work well with the variation.