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BONE HEALTH AND ENDOCRINE THERAPY IN BREAST OR PROSTATE CANCER
Bone Health in Adults Treated with Endocrine Therapy for
Early Breast or Prostate Cancer
Catherine H. Van Poznak, MD
OVERVIEW
Bone is a hormonally responsive organ. Sex hormones and calcium regulating hormones, including parathyroid hormone, 1–25 dihydroxy
vitamin D, and calcitonin, have effects on bone resorption and bone deposition. These hormones affect both bone quality and bone
quantity. The sex hormone estrogen inhibits bone resorption, and estrogen therapy has been developed to prevent and treat
osteoporosis. Androgens are an important source of estrogen through the action of the enzyme aromatase and may themselves
stimulate bone formation. Hence, the sex steroids play a role in bone metabolism. Breast cancer and prostate cancer are frequently
hormonally responsive and may be treated with antiestrogens or antiandrogens respectfully. In addition, chemotherapy and supportive
medications may alter the patient’s endocrine system. In general, the suppression of sex hormones has a predictable affect on bone
health, as seen by loss of bone mineral density and increased risk of fragility fractures. The bone toxicity of cancer-directed endocrine
therapy can be mitigated through screening, counseling on optimization of calcium and vitamin D intake, exercise, and other
lifestyle/behavioral actions, as well as the use of medications when the fracture risk is high. Maintaining bone health in patients who
are treated with endocrine therapy for breast and prostate cancer is the focus of this review.
In the United States, approximately one in eight women
will be affected by breast cancer and one in seven men will
be affected by prostate cancer. Screening techniques and excellent
therapies exist for both of these cancers. Although
there remains room for improvement, the cure and survival
rates for both of these cancers are high. It is estimated that
there are more than 2.8 million breast cancer survivors and
more than 2.7 million prostate cancer survivors alive today in
the United States. 1,2 Breast cancer and prostate cancer are
frequently hormonally responsive and may be treated with
antiestrogens or antiandrogens. In general, the suppression
of sex hormones during cancer therapy has a predictable
affect on bone health, as seen by loss of bone mineral
density and increased risk of fragility fractures. Hence, in
terms of survivorship of these patients, long-term bone
health issues, including osteoporosis, are a public health
concern.
When treating breast and prostate cancer in the adjuvant
setting, the goals of care are curative. For metastatic breast or
prostate cancer, the goals of care are palliative. Metastatic
breast and prostate cancers typically affect life expectancy
and often cause bone metastases. Although the following discussion
of bone health includes much that is applicable to
both adjuvant and metastatic care, the focus is on the nonmetastatic
setting.
OSTEOPENIA AND OSTEOPOROSIS IN THE OLDER
ADULT POPULATION
In the United States, approximately 10 million people have
osteoporosis and an additional 43 million have low bone density.
3,4 Low bone mass correlates with an increased risk for
fracture, and fractures are associated with substantial morbidity
and mortality. Approximately one in two women and
one in fıve men in the United States will experience an osteoporotic
fracture. 3 A particularly disconcerting fact is that a
hip fracture is associated with 8% to 36% excess mortality
within 1 year. In addition, 20% of patients with a fracture of
the hip require long-term nursing home care, and 60% will
not regain their prefracture level of independence. 3 In addition
to the pain and suffering associated with fractures, they
are also is a substantial burden to health care expenditure.
A standard technique for measuring bone mineral density
(BMD) is dual energy X-ray absorptiometry (DXA). The
World Health Organization 5 has defıned conditions of low
bone mass using BMD as outlined in Table 1. The T score
represents the standard deviation from an ideal bone mass.
The BMD measurement provides the diagnostic criteria of
osteoporosis as well as a threshold for pharmaceutical intervention.
4 Although the T score provides the operational definition
of osteoporosis, the underlying health concern is the
risk for fracture, not simply having a low DXA T score. There
From the Department of Internal Medicine, Division of Hematology/Oncology, University of Michigan, Ann Arbor, MI 5848.
Disclosures of potential conflicts of interest are found at the end of this article.
Corresponding author: Catherine Van Poznak, MD, Department of Internal Medicine, Division of Hematology/Oncology, University of Michigan, 1500 E Medical Center Dr., Ann Arbor, MI 48109;
email: cvanpoz@med.umich.edu.
© 2015 by American Society of Clinical Oncology.
asco.org/edbook | 2015 ASCO EDUCATIONAL BOOK
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