SAN FRANCISCO — If the first bone density reading after starting bisphosphonate therapy shows bone loss, don't stop or alter therapy, Steven R. Cummings, M.D., advised at a meeting on osteoporosis sponsored by the University of California, San Francisco.
In all likelihood, the therapy is working, but “noise” in the bone density test results in a lower density measurement. The next time the patient's bone density is taken, it probably will be higher, said Dr. Cummings, professor emeritus of epidemiology and biostatistics at the university and director of clinical research at the California Pacific Medical Center Research Institute.
He and his associates analyzed data from the 6,459-patient Fracture Intervention Trial and found that among women who lost at least 4% of hip bone density in the first year of treatment with alendronate, 92% gained an average of 5% of hip bone density in the second year of therapy.
The study involved postmenopausal women, aged 55 to 80 years, who were randomized to receive alendronate at 5 mg/day for 2 years and 10 mg/day thereafter, or placebo for up to 4.5 years.
“If you were to change treatment or add another drug” after that first follow-up, “they would gain bone and you would look like a hero, but in fact they would have improved even without” any changes, Dr. Cummings said.
Among women who participated in the study and who gained up to 4% of hip bone density in the first year on alendronate, 67% continued to gain an average of 1% bone density in the second year on therapy.
Of the women who gained a lot of hip bone—8% or more—the first year, 64% lost an average of 1% of hip bone the second year. So patients with the largest gains in bone density during the first year ought to be told: “Watch out—the next year you're likely to lose bone,” he said.
Continuing therapy also is important for reducing the risk of fracture. A comparison of the 18% of women who lost bone after a year of alendronate with the 18% of women who lost the most bone while on placebo indicated a 50% reduction in fracture risk among patients who gained bone density on treatment.
A slightly greater reduction in fracture risk was seen in those women who lost as much as 4% of bone if they were taking alendronate, compared with placebo.
The greatest overall benefits of the therapy occurred in women who lost more than 4% of bone density during the first year. In members of this subgroup, taking alendronate reduced the risk of fracture by about 80%–90%, compared with placebo.
“Stopping treatment in those patients who lose bone is exactly the wrong thing to do,” said Dr. Cummings, who also works as a consultant and speaker for two companies that manufacture bisphosphonate medications.
If a patient consistently loses bone density over multiple follow-up measurements in a period of years, then it would be reasonable to reassess treatment options, Dr. Cummings advised.