How Do Doctors Know Your Osteoporosis Treatment Is Working?

When doctors are testing a new osteoporosis drug, they do big research projects. The last step is a clinical trial. A trial is a test comparing two large groups of people. The experimental group gets the active drug. The control group gets a placebo - a fake pill that looks like the active drug.

Because osteoporosis takes so long to develop, these trials must run for three to five years. At the end, the doctors check on how many people in each group developed a fracture - the broken bones that are the hallmark of osteoporosis. If there's a big, significant difference, then they know the drug has worked.

But along the way, while the clinical trial is in progress, they check something else: bone mineral density (BMD). Because the density of bone is a big factor in bone strength. When you lose density, you are more likely to fracture. That's why your doctor tells you to drink milk and take calcium supplements - calcium helps build strong bones.

So while fewer fractures are the "gold standard" for judging the value of anti-osteoporosis drugs, doctors also look at increased BMD as a guideline for shorter term results.

BMD is measured by a simple test called DEXA. DEXA is often recommended for:

• women at menopause to check their baseline BMD;
• anyone over 50 who has a fracture to see if osteoporosis is present;
• those taking anti-osteoporosis medication to see how you are doing.

But a recent study[1] by Dr. R. Lindsay and his colleagues showed that the benefits of one drug may lower fracture risk even when there is little improvement in BMD.

The doctors decided to do the study because of other research that looked at a class of drugs called bisphosphonates. These include risedronate (Actonel) and alendronate (Fosamax). That work suggested that less than 20% of reduction in fractures seen in patients taking these drugs could be explained by their increases in BMD.

Dr. Lindsay wanted to check that out. So he and his colleagues reviewed the results of clinical trials of nearly 9,000 patients taking risedronate or placebo. They looked at the BMD and fracture results. And it was true.

In patients taking risedronate:

• Even a small increase in BMD seemed to reduce fracture risk - but
• Larger increases in BMD did not necessarily yield larger decreases in fracture risk.

So there may be a threshold above which further increases in BMD have little effect on fracture benefit.

For doctors, this means that more research needs to be done to find out what else is going on to influence fracture - such as the architecture of bone.

But what does this mean for you?

If you are on medication to treat or prevent osteoporosis, your doctor may recommend DEXA every year or two. How do you feel about the results? Do you worry if the DEXA does not go up a lot?

This research says, "Don't worry."

The researchers concluded that the lack of a significant change in BMD does not mean that anti-resorptive therapy is not working. As long as the BMD does not fall, your therapy need not be changed.[2]