The drug relieved all pain in 19 of the 85 patients whose prostate cancer had become resistant to hormone treatment. "All of the patients were in the final stages of prostate cancer," says lead researcher Axel Heidenreich, MD, a Professor in the Urology Department at Philipps-University in Marburg, Germany.
Hormone therapy is the standard treatment for men with advanced prostate cancer but most develop resistance to it within 18 to 36 months. At that point, treatment shifts to measures that relieve pain and improve quality of life. Pain is a major symptom for the 90% to 95% of advanced prostate cancer patients whose cancer eventually spreads to the bone.
Patients in the study assessed their bone pain on a scale of zero to 10 before treatment and every two weeks during the trial. They kept taking whatever pain medications they were already taking, adjusting dosages as needed to control pain.
Patients Rate Their Pain
Before treatment, the average pain score of 85 patients participating in the study was 7.9. That score dropped to an average of 2.5 for the 64 patients (75%) who responded to the drug. Nineteen of these 64 patients were entirely pain-free and stopped taking all other pain medications. Another 45 patients significantly decreased their need for other pain medication during the study. The relief from clodronate appeared after about four days of therapy. On average, clodronate continued to provide relief from pain until the patients? last three weeks of life.
Patients started with 300 milligrams (mg) daily by intravenous infusion for eight days, followed by oral doses of 1,600 mg daily. The only significant side effect was stomach upset from taking the drug orally in 18% of patients. "This is a very effective palliative therapy with very limited side effects," Heidenreich says. "Newer generation bisphosphonates in pilot studies show the same clinical effect with essentially no side effects at all."
Clodronate relieves pain by inhibiting the abnormal absorption of bone tissue caused by spread of cancer cells, thereby allowing the bone to heal itself. Other bisphosphonate drugs are widely used to treat osteoporosis and other noncancerous bone diseases.
Other Drugs Under Study
Several previous studies have found clodronate and pamidronate, another bisphosphonate drug, are helpful in relieving pain from cancers that start in or spread to the bones. Pamidronate has already been approved by the U.S. Food and Drug Administration for treatment of patients with multiple myeloma (a cancer that starts in the bone marrow) or with breast cancer that has spread to bones.
"I?m very impressed with the results of this study," says Herman Kattlove, MD, Medical Editor for the American Cancer Society. "Patients seem to have gotten wonderful pain relief, though you don?t know how much placebo effect is involved. This should generate larger studies that compares one group of prostate cancer patients who receive a bisphosphonate drug to an otherwise similar group who do not."
More research is already underway. For example, a group of Canadian researchers is currently comparing mitoxantrone (a chemotherapy drug) alone or mitoxantrone plus clodronate. And, Heidenreich and his group launched a trial of ibandronate, a new-generation bisphosphonate, in late 2000. The first 25 patients in a pilot study reported similar pain relief to those in the clodronate study, with one major difference: patients had no significant side effects, including stomach upset. Final trial results should be available in early 2002.
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