New Study Shows Importance of Treating Secondary Causes of Bone Loss in Breast Cancer Patients
By John Schieszer
Bone loss is a growing concern among breast cancer survivors, because aromatase inhibitors are increasingly being prescribed as adjunctive hormonal therapy for estrogen receptor–positive breast cancer. Research shows significant decline in bone mineral density (BMD) and increased risk of fracture among women who receive aromatase inhibitors. However, researchers are now reporting that bone loss can be prevented in breast cancer survivors undergoing hormonal therapy if secondary causes of bone loss (vitamin D deficiency, idiopathic hypercalciuria, primary hyperparathyroidism, hypocalciuria, and normocalcemic hyperparathyroidism) are corrected and bisphosphonate therapy is used appropriately.
Primary causes of osteoporosis are menopause and aging. Secondary causes are diseases or conditions that exacerbate bone loss.
"Doctors evaluating breast cancer patients for possible bone loss should look further than cancer drugs," said Pauline Camacho, MD, an associate professor of medicine at Loyola University School of Medicine, Chicago.
It is well documented that aromatase inhibitors can decrease BMD and increase the risk of fractures in postmenopausal women. These medications can decrease the body's production of estrogen. Although estrogen feeds cancer, the hormone also protects against osteoporosis.
Camacho and colleagues reviewed charts of 81 consecutive breast cancer patients who were referred for treatment or prevention of osteoporosis. The researchers found that 51 patients had secondary causes of bone loss, including vitamin D deficiency (65%), excessive calcium excretion in urine (16%), or an overactive parathyroid gland (13%). Thirty patients did not have secondary causes of bone loss.
All the patients received similar treatment with osteoporosis medications, such as alendronate and ibandronate. Women with secondary bone loss, however, also received additional treatments. For example, vitamin D deficiency was treated with prescription doses of vitamin D supplements, and excessive calcium excretion was treated with a diuretic.
After 1 year, the breast cancer patients with secondary causes of bone loss had stable BMD in their spines and necks. BMD improved in the breast cancer patients who did not have secondary causes of bone loss. BMD is the amount of calcium and other minerals packed into a segment of bone and it predicts osteoporosis.
Camacho said the study demonstrated that bone loss "can be prevented in women undergoing hormonal therapy if secondary causes of bone loss are corrected and bisphosphonate osteoporosis drugs are appropriately used." She said the mean age of the women with secondary causes of bone loss was 58 years, and the mean age of the women without secondary causes of bone loss was 63 years.
These study findings, which were presented at the 31st annual meeting of the American Society for Bone and Min eral Research, suggest that healthcare providers should discuss the importance of treating secondary causes of bone loss with women undergoing breast cancer therapy.
"This study is good news for breast cancer survivors, because they are worried about their bones and so are their oncologists. We showed that with proper workup and appropriate treatment they do quite well in terms of bone health. So our findings are quite reassuring," said Camacho in an interview with The Oncology Pharmacist. "I think the most important take-home point here is that aromatase inhibitors are being used increasingly in breast cancer patients and so these patients need to be thoroughly evaluated and evaluated for secondary causes of bone loss, such as calcium deficiency. We found vitamin D deficiency was the most common problem. We saw it in 65% of the patients."
