Are You at Risk for Osteoporosis?
by Rena Vassilopoulou-Sellin, MD, and Charles Stava, MHSA
The exact prevalence of osteoporosis among survivors of cancer is not well understood, but bone loss is a relatively common occurrence during cancer treatment. It also may linger for many years, placing cancer survivors at heightened risk for osteoporosis. Osteoporosis is a condition defined by a decrease in bone mass and strength, which results in an increased susceptibility to fractures. The skeletal system is a dynamic organism in which bone is constantly remodeling itself; older bone is resorbed and new bone deposited in its place. Osteoporosis occurs when the degree of bone resorption exceeds that of bone formation.
Age, lifestyle, and hereditary factors, as well as nutrition, hormonal status, and medications, contribute to the development of osteoporosis. Cancer therapies may heighten a person’s risk. Various chemotherapy and radiation regimens, especially if they induce hypogonadism (a defect of the reproductive system that results in lack of function of the ovaries or testes), can accelerate bone loss and osteoporosis.
Dr. Rena Vassilopoulou-Sellin
In many cases, the cancer cells may invade the bone marrow space (as in hematologic malignancies or metastases from solid tumors) and cause deterioration of bone mass. Malignancies of the gastrointestinal track may require resection of significant sections of the intestine or stomach, which may in turn interfere with absorption of calcium or Vitamin D, thus increasing the risk of bone loss. Alternatively, many treatment regimens include cortisone-like drugs (glucocorticoids) intended to alleviate the treatment toxicity or to reduce the inflammation or swelling caused by the tumor. Glucocorticoids induce bone loss by interfering directly with bone turnover and indirectly with calcium absorption and gonadal (ovaries and testes) function.
Various chemotherapy and radiation regimens can accelerate bone loss and osteoporosis.
Osteoporosis Risk for Breast Cancer
Women with breast cancer may be at increased risk of bone loss because of chemotherapy-induced early menopause. In addition, women with hormone-sensitive breast cancer are treated with potent estrogen antagonists, aromatase inhibitors, which exacerbate the negative effects of a decrease in estrogen on bone health. Fortunately, several non-estrogen agents are available that can both prevent and treat osteoporosis in this group.
Osteoporosis Risk for Prostate
Prostate cancer is generally considered to be testosterone dependent, and medical or surgical castration to suppress testosterone levels is often the mainstay of treatment. Both can induce androgen deprivation for many years and can cause excessive bone resorption and, in time, osteoporosis. In addition, prostate cancer usually affects older men who may already have decreased bone mass at the time of diagnosis. Fortunately, there is increased awareness of the problem in recent years, resulting in improved surveillance to detect bone loss and in vigorous evaluation of non-testosterone therapeutic options for men with prostate cancer and testosterone deficiency.
Osteoporosis Risk for Childhood
Thanks to improved cancer detection and cancer therapies, children diagnosed with malignant diseases are surviving and living longer. However, many therapies used to treat childhood malignancies, such as chemotherapy, glucocorticoids, and radiation, can affect bone growth during the formative years of childhood and adolescence. As childhood cancer survivors reach adulthood with diminished bone mass, they may be at increased risk for osteoporosis later in life. In addition, cranial irradiation can affect the pituitary gland, resulting in lasting deficiencies of gonadal and growth hormones, further exacerbating the problem. Careful surveillance can provide early detection, thus allowing for appropriate intervention strategies.
Fortunately, people are living longer after cancer diagnosis and reaching their elderly years, during which bone loss is naturally more common. Bone mineral density should be measured on a regular basis to promote early detection and prompt treatment before osteoporosis becomes severe enough to result in fracture. Of course, attention to nutrition and lifestyle approaches remains very important in cancer survivors.
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Dr. Rena Vassilopoulou-Sellin is a clinical professor in the department of Endocrine Neoplasia and Hormonal Disorders, and Charles Stava is a cancer researcher, both at the University of Texas M. D. Anderson Cancer Center in Houston, TX.
This article was originally published in Coping® with Cancer magazine, March/April 2009.