Effect of letrozole versus placebo on bone mineral density in women with primary breast cancer completing 5 or more years of adjuvant tamoxifen: a companion study to NCIC CTG MA.17.
Aromatase inhibition depletes estrogen levels and may be associated with accelerated bone resorption. The National Cancer Institute of Canada Clinical Trials Group (NCIC CTG) study MA.17B evaluated bone turnover markers and bone mineral density (BMD) in postmenopausal women randomly assigned to MA.17, a placebo-controlled trial of letrozole after standard adjuvant tamoxifen.
Eligible women had a baseline BMD T score of at least 2.0 in either the hip or L2-4 spine; all received calcium 500 mg and vitamin D 400 U daily. Percentage change in BMD (L2-L4 spine and hip) at 12 and 24 months, rate of osteoporosis, and change in markers of bone formation (serum bone alkaline phosphatase) and resorption (serum C-telopeptide and urine N-telopeptide) at 6, 12, and 24 months were compared.
Two hundred twenty-six patients (122 letrozole, 104 placebo) were enrolled. Baseline characteristics were similar in the two groups, including BMD, median age of 60.7 years (81%