Bone health is an important issue for all women, and one area of special concern for women with breast cancer. Currently, almost half of American women who live to age 80 develop postmenopausal osteoporosis, a disease in which the bones become thin and fragile due to estrogen deficiency and aging. This disease can be prevented by long term estrogen replacement therapy, but the treatment has recently lost favor because it carries an increased risk of heart attacks, stroke and breast cancer. Postmenopausal women who have already had breast cancer are not only advised not to take estrogen, which might encourage a recurrence of their cancer, but are also often given agents such as adjuvant chemotherapy or aromatase inhibitors which may aggravate bone loss. Premenopausal women with breast cancer become at risk for an early onset of bone loss if they undergo chemotherapy-induced premature menopause.
When I consult with a woman who has had breast cancer about her bone health, I begin by asking what questions she would like to have answered so that I can be certain to address those concerns specifically. Then, I perform a comprehensive health assessment. This includes asking about her health history, reviewing any available prior laboratories and bone mineral density (BMD) tests, performing a directed physical examination and ordering selected tests. This evaluation serves several purposes.
First, it helps me to understand why her BMD is at its current level. For example, a woman in her fifties may have low BMD not because she is recently menopausal but because she had anorexia as a teenager. After all, the bone density we have today reflects both the amount of bone we managed to accrue during childhood and adolescence, and the amount that we may have lost since then.
At this point, I often find it is helpful to explain how a bone density test is interpreted. Briefly, BMD is evaluated by comparing a patient’s BMD to a gold standard, namely the BMD of young normal women of the same ethnicity. Any difference in BMD can be expressed as a percentage or scored using a statistical term, the T-Score. A T-Score difference of 1.0 roughly corresponds to a difference of 10%, so that if a patient has a T-Score of -2.0, it means she has a BMD which is roughly 20% less than the average BMD of young women. It does not mean that she has lost 20% of her bone. She may have had the same low BMD since she achieved her peak mass in her twenties. BMD is classified according to the T-Score: less than -2.5 is osteoporosis; better than -1.0 is normal; scores between normal and osteoporosis are in a grey zone which is called “osteopenia”.
A patient’s BMD also can be compared to the average BMD of women her age, and this is called the Z-Score. This comparison is helpful because if a patient’s Z-Score is 0.0 it suggests her BMD is exactly what would be expected for someone her age. However, if it is less than -1.0, this suggests that there may be factors other than estrogen deficiency and age which are contributing to her low BMD. Thus, in the next phase of evaluation, I try to determine if there are any such factors present that potentially could be corrected or mitigated. These include inadequate calcium/vitamin D intake, smoking, excessive alcohol consumption, certain prescription drugs, and unsuspected disease. Such conditions can usually be determined from the patient’s medical history and a few simple laboratory tests.
Once an evaluation of BMD is completed, I decide whether to recommend treatment with prescription drugs. Guidelines developed by the National Osteoporosis Foundation suggest that if the T-Score is less than -2.0, pharmacologic therapy is advisable. However, the decision to use prescription drugs needs to be individualized. For example, if two women have the same low BMD, but one has stable BMD and has never had a fracture, and the other is rapidly losing bone or already has had a fragility fracture, the latter has a higher risk of future fracture because the microarchitecture or quality of her bone is likely to be more abnormal. Likewise, the optimal level of bone density for a slender woman at risk of falls because she is an avid skier would be higher than for a heavier, sedentary woman.
If I believe drug therapy is advisable, I first explain that the foundation of all osteoporosis therapy is a balanced diet, adequate intake of calcium and vitamin D, a healthy lifestyle (including weight-bearing exercise and the avoidance of smoking or excessive alcohol), and fall prevention. Between diet and supplements, a woman should achieve a daily intake of around 1500mg of calcium and 800 International Units of vitamin D. The goal is to avoid deficiency of these nutrients; it is not helpful and may even be harmful if too much is consumed. The role of weight-bearing or resistance exercise in an adult is not so much to build bone (it is only in adolescence that such exercise leads to a substantial increase in bone mass) but rather to prevent falls by building strong muscles and enhancing balance. I illustrate the importance of using common sense to avoid falls by explaining that biomechanical calculations predict that even if a woman has normal BMD, she would be likely to fracture her hip if she fell sideways on to a hard surface and was unable (perhaps because she fainted) to break her fall. The reason most middle-aged women do not fracture is not so much because their BMD is normal but because they do not have serious falls.
Next, I review the pros and cons of the various prescription drugs commercially available, indicate which treatment I think would be best that woman, and then let her choose. Fortunately, there are several drugs which can prevent bone loss, improve bone density and bone mass, and significantly reduce the risk of fractures. If woman cannot tolerate a particular drug, I usually can find an alternative one.
Finally, whether or not I have initiated pharmacologic therapy, I recommend a strategy for follow-up. This may include blood or urine tests in a few months to see if the new drug is affecting bone metabolism as expected and/or a second bone density exam in one to two or more years, with the one year interval being recommended only for those initiating therapy or with precariously low BMD.
In summary, I recommend that a woman with breast cancer work with her physician to answer the following questions:
- What is her BMD?
- If her BMD is low, why?
- What measures can she take on her own to preserve bone and prevent fractures?
- Should she take prescription drugs?
- Which drug would be best for her?
- When and how can she be sure her therapy is working?
At the end of a consultation, I like to be certain that all of a woman’s questions are answered, and to exchange contact information in case future questions arise. It gives me great satisfaction to empower patients with the knowledge they need to make optimal decisions about their bone health.
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