Secondary causes of low bone mass in patients with breast cancer: a need for greater vigilance

An observational study to assess the prevalence of secondary causes of low bone density in patients with breast cancer.

Female patients within 5 years of breast cancer diagnosis and age older than 50 years at diagnosis were recruited. Consenting patients completed a questionnaire and had blood taken for serum calcium, vitamin D, parathyroid hormone (PTH), and thyroid function testing. Bone mineral density (BMD) was assessed. Abnormalities were additionally investigated and treated.

Two hundred patients were recruited. The median age at diagnosis was 62 years. One hundred sixty-nine patients had hormone receptor (HR) -positive cancer. Vitamin D and thyroid function were assessed in 200 patients; PTH was assessed in 197 patients; and BMD was assessed in 187 patients. Eighty-seven patients (46.5%) had osteopenia, and 24 patients (12.8%) had osteoporosis. Vitamin D levels were insufficient (ie, 50 to 75 nmol/L) in 74 patients (37%) and were deficient (ie, < 50 nmol/L) in 54 patients (27%). Only 24 of 65 patients taking vitamin D supplements were replete (ie, > 75 nmol/L). Thirty-nine (21%) of 197 patients had PTH concentrations greater than the normal range. Six had primary hyperparathyroidism (PHPT), and two more had recent surgery for PHPT. Twenty-seven had secondary hyperparathyroidism (HPT) from vitamin D deficiency and six had normocalcemic HPT. Of 90 patients with low BMD and HR-positive cancer, 8% (seven of 90 patients) had new or recent PHPT, and 63% (57 of 90 patients) had insufficient or deficient vitamin D. More patients with HR-positive cancer than with HR-negative cancer had elevated PTH (38 of 167 v three of 30 patients, respectively; P = .10).

Secondary causes of low BMD are common in postmenopausal women. Identification and management of secondary causes should be included in bone health management algorithms.