Aromatase inhibitors are recommended for and widely used as anti-estrogen therapy for postmenopausal women. Numerous studies have shown that these drugs anastrazole (Arimidex), letrozole (Femara), and exemestane (Aromasin) are effective in reducing the risk of a breast cancer recurrence in women with early-stage disease. They also have a well-known side effect: bone loss.

After it became clear that bone loss was a common side effect, many oncologists began to routinely prescribe bisphosphonates drugs that can help prevent bone loss to their patients who were on an AI. The thought was that these drugs, like alendronate (Fosamax) and zoledronic acid (Zometa), would keep women on an AI from developing osteoporosis. It was also thought—and some studies had suggested that a bisphosphonate might reduce the risk of a woman developing bone metastases.

But should all women on an AI be taking a bisphosphonate? The answer appears to be no.

In the current issue of the Journal of Clinical Oncology, researchers reported findings from an analysis that explored whether it was more beneficial to give all women on an AI a bisphosphonate; to screen all women (initially and/or annually) and treat those found to have osteoporosis; or to screen all women (initially and/or annually) and treat those found to have osteopenia.

The end result: The most effective approach (health-wise and cost-wise) is to screen women annually and then prescribe a bisphosphonate to the women who are found to have osteoporosis. This is the same approach we use to determine if a healthy woman should start on a bisphosphonate we wait until the problem is seen before giving the drug. (A recent study suggested that annual screening is not recommended for healthy women.)

What about the idea that taking a bisphosphonate will reduce a woman’s risk of developing metastatic disease? This idea made sense, in theory. But, to date, the data haven’t shown any benefit. As the authors of this recent study note, a recent meta-analysis of 13 clinical trials and 7,000 patients found that taking a bisphosphonate did not decrease a woman’s chances of developing bone metastases, having a recurrence, or dying of breast cancer.

This is yet another example of how quickly we often are to jump at ideas that sounds good, rather than wait for the evidence to show us what works.

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6 Responses to Aromatase Inhibitors and Bone Loss

  1. Olga says:

    (From the source) “In subgroup analyses, use of zoledronic acid was associated with a statistically significant lower risk for disease recurrence” – that means that zoledronic acid CAN be affective in lowering risk for recurrence. Also the trails included women with different types of breast cancer, and it was already shown that bisphosphonates are effective for a particular subgroup of women – ER positive and with suppressed estrogen level. One medicine can’t work for all types of breast cancer – and the effect of bisphosphonates is lost in the trials mega-analysis as non-statistically significant because it was not presented for sub-groups

  2. I was on an AI after my other breast cancer treatments ended, and I developed osteopenia. My OB/GYN put me on Fosamax, and three years later, I am happy to report my bone density is in the normal range.

    Studies are invaluable, but sometimes we should also rely on the art of medicine.

  3. Lisa Ellis says:

    Beth, as your doctor’s treatment corresponds to the study recommendations, I don’t understand your statement about the need to rely on the art of medicine. If I am going to take a medication, I want to know about the benefits versus risks. I take arimidex and I am glad to see the study confirms my onc’s recommendation – to avoid taking a taking a biophosphonate. unless indicated. When I started arimidex my bone density was above normal. I’ll have another bone density test this fall & go from there.

  4. Jonathan says:

    the silver lining in all of this is that much of the bone loss women experience on AIs is reversible after their 5 years of treatment ends, and their bones are pretty much the same as those who never took the drugs. Bispohosphonates are riskier than once thought and the side effects are not worth it for many of the younger women with breast cancer who will not suffer a fracture while taking an AI. I have a great aunt, aged 83, who lost all of her teeth on Fosamax and my uncle’s wife who is 61 experienced a pathological fracture of the femur 2 years ago while on Actonel that STILL hasn’t healed properly!

  5. Heriberto Gordon says:

    This medical bone density is not the true physical “density” of the bone, which would be computed as mass per volume. It is measured by a procedure called densitometry, often performed in the radiology or nuclear medicine departments of hospitals or clinics. The measurement is painless and non-invasive and involves low radiation exposure. `^….

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  6. Beth Gainer says:

    Lisa, I also believe in weighing the risks and benefits of medicine. Studies are highly valuable. However, medicine is an art, too. My doctors had the studies to back their decisions about my medical treatment, but they also treated medicine as an art — and instinct that this was the right treatment plan. Medicine is both an art and a science.

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