This week, Dr. Sydney Spiesel discusses two promising new treatments: one for cancer and another for osteoporosis.
The benefits of radioimmunotherapy
Concept: Radioimmunotherapy is an exciting but elusive new treatment for cancer. The idea is clever: Make tightly targeted antibodies that can bind to specific sites on the surface of tumor cells. Then bind intensely radioactive material to these antibodies. Injected into a patient, the radioactive antibody molecules home in and attach to the targeted sites, and destroy the malignant cells by spraying them (and other nearby tumor cells) with lethal radiation.
Treatments: Two such radioactive-antibody cancer medications exist: Bexxar and Zevalin. As the drug Rituxan, which consists of the antibody without the radioactivity, they are already widely used for non-Hodgkin's lymphoma and other cancers. With the radioactivity, Bexxar and Zevalin can be used to treat patients with lymphoma even if they have developed resistance to Rituxan. Similar products (made with different monoclonal antibodies) have shown promise for the treatment of brain cancer, breast cancer, and lung cancer.
Effects: Bexxar and Zevalin cost approximately the same—a staggering $25,000 to $30,000 for the roughly weeklong treatment. Both have worked for some patients, apparently leading to long-term remissions. Both also can cause dangerous, even lethal, reactions and side effects, though that is rare.
Comparison: The two treatments have not been tested head-to-head, so we have no idea of their comparative effectiveness, but we know of some differences between the two products. The body clears the radioactivity of Bexxar more quickly than that of Zevalin. On the other hand, Bexxar's radioactivity has the potential for harming the thyroid gland and may even pose risks to people in close contact with the patient shortly after the drug is administered. Also, patients are more likely to develop an allergic reaction to it. Zevalin, however, must be made up by a specially trained radio-pharmacist, working near the location where the medicine will be administered, because the half-life of its radioactive isotope is short.
Problem: This promising line of treatment is underutilized. One reason is simple unfamiliarity. Another is patients' general fear of radioactive materials. And a third reason is lack of training among oncologists, the doctors who work daily with patients with tumors, in the use of radioactive materials. In general, this kind of work is done by specialists in nuclear medicine. We need to train more oncologists in this method.
Strengthening weak bones
Condition: Osteoporosis is a medical condition in which the bones lose some of their calcium and weaken as a result. An estimated 24 million people in the United States (and well over 250 million worldwide) suffer from this condition. The great majority are women over the age of 45. The bone weakness caused by osteoporosis increases the risk of fractures. The cost of these broken bones is high: more than $18 billion a year just for medical costs in the United States.
Standard treatment: The treatment for osteoporosis has become standardized to a certain extent: oral medications in the bisphosphonate class, often taken along with calcium and vitamin D. Bone is constantly being remodeled over our lifetimes, to repair injuries and to accommodate growth and physical stress. For the remodeling to occur, cells called osteoclasts delicately remove the mineral part of bone, a process called resorption. Other cells, osteoblasts, work nearby to build up bone, but sometimes not as quickly as the osteoclasts take it down. When that happens, often as people age, bones gradually become depleted of calcium. Bisphosphonates work by inhibiting the activity of the osteoclasts. Despite bisphosphonate treatment, however, osteoporosis and the fractures it promotes continue to be a serious problem.
New findings: A recent research report by Dennis Black of the University of California, San Francisco describes a promising alternative treatment with another drug, Aclasta. It, too, interferes with osteoclast function, and needs be given only once a year by a 15-minute intravenous injection. Black's team reports on an experiment in which almost 4,000 women received the treatment (and were compared with a matched group of about the same size). The results were impressive. Compared with women in the placebo group, the treated women, followed for three years, showed a dramatic decrease in fractures of the spine, the hips, and other bones. In addition, treatment with Aclasta significantly increased bone density, a marker for calcium content and often a sign of increased bone strength.
Caveat: There was little difference in troublesome side effects between the two groups of women. The exception was this: 1.3 percent of the Aclasta-treated patients had atrial fibrillation, a serious heart-rhythm disturbance, compared with 0.5 percent of the other women. Still, the treated patients were not more likely to die than the other group.
Conclusion: Despite the relatively rare side effect, this new treatment is clearly better than the one many women are presently taking. It is likely to improve the quality of life for a great many people.