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The Dark Side of Aromatase Inhibitors, Part 2

The Dark Side of Aromatase Inhibitors – Part 1

I decided to divide this topic up into a couple of posts because as you may or may not know, I’m working on being less wordy and more concise in my writing. Part one will be my attempt to convey some general information about aromatase inhibitors and part 2 will be more focused on my personal experience – rant, so stay tuned.

You might want to read and download, Endocrine Therapy – Managing & Making Decisions About Your Aromatase Inhibitor Medication.

Many breast cancer tumors are estrogen positive (ER-positive), progesterone positive (PR-positive), or both (ER-positive and PR-positive). Mine was both.

By the way, this information about your tumor(s) is provided in your pathology report, and you simply must have a copy of this report in your possession so you can familiarize yourself with your own unique cancer’s biology, even though this might sound like the last thing you want to do after your diagnosis.

Be sure to ask for a copy if you don’t receive one.

If a woman is ER and/or PR positive, her oncologist might very likely prescribe an aromatase inhibitor after surgery, chemotherapy or radiation as part of her adjuvant therapy treatment plan. The intent is, of course, to prevent recurrence.

There are three kinds of aromatase inhibitors (referred to as ‘AIs’ from here on out) that have been FDA approved:  anastrozole (Arimidex®), letrozole (Femera®) and exemestane (Aromasin®).

Basically, these drugs block tumor growth by lowering the body’s natural supply of estrogen.

How do they do this?

These drugs don’t allow the food supply (estrogen) to get to the tumor because they block the aromatase enzyme, which is needed for the production of estrogen.

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Hence the name, aromatase inhibitors.

AIs are often prescribed for post-menopausal women because they don’t block estrogen produced by the ovaries, but do inhibit estrogen production in other body tissues. If you’re not post-menopausal, the benefit’s not there. For pre-menopausal women with estrogen positive cancers, Tamoxifen is still the recommended hormonal adjuvant therapy drug most often prescribed.

Before cancer, I didn’t even know that in addition to the ovaries other body tissues also produce estrogen, but they do.

As I understand it, there isn’t a lot of difference between the three AI drugs. One difference however, is that Aromasin® is an irreversible aromatase inhibitor (stops aromatase enzyme’s production process permanently) while the other two are not. Studies seem to indicate the effectiveness of the drugs in preventing recurrence is pretty much the same.

AIs have become standard treatment for adjuvant hormonal therapy for many post-menopausal breast cancer patients; gotta shut that estrogen production line down – and that’s what AIs do.

I clearly remember the day when oncologist number one showed Dear Hubby and me all those mind-boggling, ten-year survival odds charts. The charts ‘said’, that if I agreed to add Arimidex® as part of my adjuvant treatment plan, I would supposedly gain another six percentage points for my staying-alive plan.

I was on board. I wanted those additional six percentage points on my side.

Who wouldn’t?

And now on to the dark side of AIs – in case you can’t guess, but I’m betting you probably can, this would be the nasty side effects.

Every person is different. Just because you’ve heard horror stories about unpleasant side effects, don’t assume you’ll experience the same.

Having said this, some of the side effects are fairly common and even somewhat predictable.

Generally speaking and maybe even mildly comforting to know (then again maybe not), the side effects of all three AIs are similar.

The main and most often complained about side effects are:  joint pain, bone loss, bone fractures, lowered libido, hair loss/thinning, weight gain, hot flashes and sleep issues to name a few. (Yikes, do we really need more?)

The side effects are often not addressed adequately, if at all, by oncologists. This is too bad because side effects can, at the lesser end of the spectrum, be highly annoying and at the worst end, extremely debilitating.

I speak from experience on this as I have had some very unsettling side effects myself.

More on this to come.

In fact, side effects (mine anyway) will be the focus of The Dark Side of Aromatase Inhibitors – Part 2.

Stay tuned and get your rants ready!

Note:  Please remember that while I always strive for accuracy in facts I share, my posts also generally include my thoughts and opinions and are not intended to be medical advice specific to you. Please discuss all concerns with your doctor.

Are you on an aromatase inhibitor or do you know someone who is?

Are you on Tamoxifen?

If so, how are things going and are the side effect issues (if you have any) being adequately addressed?

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You might want to read and download, Endocrine Therapy – Managing & Making Decisions About Your Aromatase Inhibitor Medication.


The dark side of aromatase inhibitors, part 1
The Dark Side of Aromatase Inhibitors



334 thoughts to “The Dark Side of Aromatase Inhibitors – Part 1”

  1. Do all these breast cancer drugs pretty much have the same side effects? i’m starting exemestane, will my hair thin out eventually?….What other major side effects are caused from this drug?

    1. Teresa, Everyone reacts differently. Having said that, many women do experience similar side effects. You should receive a list of all potential side effects when you receive your medication. Remember, you might do fine. Don’t assume the worst will happen. My advice is to start a journal so you can document changes/side effects if and when they happen. My best to you.

  2. I’ve been on Aromasin almost 6 months. In the last 3 weeks my hands started tingling. Now and overnight, my thumbs have almost “locked up” and are popping like in trigger finger. The bones in one foot are also very sore. My hips were achy but have gotten better. I reported this to my oncologist and he “suggested” it may be arthritis and maybe not related to the drug. I told him it came on so suddenly! He took me off the drug for 30 days to see if that makes the joint pain go away. Since my last appointment, I’m having muscle cramps with a muscle spasm in my back–very uncomfortable. I stay on a heating pad! Do you think these symptoms are from the drug? I’m 65 and haven’t had any of these problems before now. I feel like the onco poopooed me off.

    1. I had the same experience. On Letrozole for 4 months with only minor hot flashes (I’m pre-menopausal on ovarian suppression Zoladex in order to take Letrozole.) and hip stiffness/aching that I attributed to over doing it with exercise. At month 4, my hands were stiff at night; when clenched it was very painful to pry them open. Then, at month 5, I had painful trigger finger in my ring fingers and pinkies.

      My surgeon was adamant that AIs do not cause trigger finger. She put me on a 30 day break from Letrozole during which my hips stopped aching. My hand stiffness lessened a tiny bit, but the trigger fingers persist. I demanded to be assigned to an oncologist within the clinic as I knew after surgery my surgeon would be out of the picture and no one would follow me for the AI issues. This offended my surgeon! (As an aside, my surgeon tries to play the role of oncologist, radiation oncologist and radiologist. It’s incredible: I have the latter two different docs but my surgeon argues with them!) I did finally get assigned to a medical oncologist, and he also maintains that Letrozole does not cause trigger finger. He says that the AIs create symptoms that mimic arthritis, but there really is no physical change in the joints. Then where does the stiffness come from, if it is not physical?!? For what it is worth, a Lymphedema physical therapist in my clinic said that the AIs do make joints triggery.

      My feeling is that if you know your body and you have sudden onset of Joint and muscle pain symptoms after taking AIs (even 6 months in), it is entirely plausible that they are due to the AI. The challenge is weighing the huge anti-cancer benefits against the arthritic symptoms. Some enlightened oncologists have studied how to mange the side effects and found acupuncture and exercise (moving the joints to keep them lubricated and flexible) work the best. I just wish that the other oncologists would stop poopooing our concerns and just say, “yes, this happens, but you can try the these things to manage the symptoms”. Just getting validation for our concerns makes such a difference.

  3. Ali’s. Aren’t they wonderful little pills? I took my cancer very seriously. Went through chemo for increase of 4% survival rate. Told I could add 30% to my survival rate just by taking a little pill once a day. Piece of cake I thought. I tied every single AI on the market then Tamoxafan. When on AIs I was hit with every miserable side effect including vaginal atrophy and dryness. So I was put on Tamoxafan. All good for 6 weeks then developed wild mood swings. I was alienating everyone around me including my long suffering husband. I envied the women who could tolerate these drugs. But everyone’s physiology is just so different. We are not one size fits all. If a Dr tells you it can’t be a side effect well how does he know?? We are ALL different. I got to the point of weighing up quality of life maybe ending up in a psych ward, or divorce court, and becoming a little old lady before my time. So after giving every drug my best shot and weighing up quality of life over these drugs I made the decision to go drug free and concentrate on enjoying life, happiness, energy, diet and exercise. I am 8 years cancer free now. I may get mastastic cancer and I may regret my decision but at the end of the day my Oncologist could not tell me that if it did return it was due to being off the drugs. All the drugs can do is limit chance of recurrence. It is not a guarantee.

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