Aromatase inhibitors and keeping an eye on your bones

If you have been prescribed an aromatase inhibitor, someone has probably mentioned your bones, and it may have seemed like a change of subject.

It is not. MedlinePlus, describing anastrozole, carries a plain warning: anastrozole may cause or worsen osteoporosis. It goes on to say that it can decrease the density of your bones and increase the chance of broken bones and fractures. Its advice to patients is to talk about these risks with their doctor.

That is the whole logic behind bone monitoring during this treatment. The drug that is helping to keep breast cancer away has a known effect on the skeleton, so the skeleton gets watched.

MedlinePlus describes anastrozole as used to treat early breast cancer in postmenopausal women, alongside surgery or radiation. It is also used for advanced breast cancer, and for cancer that has worsened after tamoxifen treatment.

Hormone treatment of this kind is usually taken for a long stretch — MedlinePlus notes it is taken once a day, with or without food, at about the same time each day. A side effect that builds slowly over years is a different problem from one that appears in a fortnight, and it is managed by checking rather than by waiting for symptoms.

Weak bones are silent until something breaks. That is precisely why they are measured rather than felt for.

You may have arrived here wanting a number: how often should the scan happen? The MedlinePlus entry does not give one, and inventing an interval would be worse than leaving the gap visible.

So ask. It is a short, answerable question at your next appointment: do you want me to have a bone density scan, and how often should it be repeated? Your team will factor in your age, your other risk factors and your treatment plan — things a webpage cannot know.

MedlinePlus lists common side effects of anastrozole including hot flushes, joint, bone and muscle pain, nausea and mood changes. Aching joints in particular catch people out, because it can be mistaken for arthritis or ageing rather than a treatment effect.

It also lists serious effects that need prompt medical attention: chest pain, shortness of breath, swelling and vision changes. Those are not bone issues, but they belong on your radar while taking this drug.

Bone health is one of the areas where patients can usefully be active participants rather than passengers.

• Ask whether a baseline bone density scan is appropriate before or early in treatment.
• Ask whether you have other risk factors that add to the drug's effect.
• Ask what, if anything, they recommend for bone strength while you are on it.
• Report any fall, even one that seemed minor at the time.
• Report new or worsening bone pain rather than assuming it is the usual aching.

None of this is a reason to stop the medicine on your own. It is a reason to make bones a standing item in your follow-up conversations, so that if anything is changing, it is spotted while there is still plenty that can be done about it.

• Call 911 or go to an emergency department if your lips, tongue or throat swell. Do the same for chest pain, or trouble swallowing or breathing. MedlinePlus lists all of these as serious effects.
• Call your care team the same day if you fall and cannot put weight on a limb. Do the same if a bone hurts sharply after a small knock.
• Call your care team within a day or two if your vision blurs. Also call for a fever or sore throat, yellow skin or eyes, or bone pain that is not settling.