Radiopharmaceuticals Effective Therapy for Metastatic Bone Pain

NEW YORK—“Nuclear medicine is one of the best kept secrets of medicine today,” said Stanley J. Goldsmith, MD, director, Division of Nuclear Medicine, New York Presbyterian Hospital. In a talk at a nuclear oncology conference sponsored by Memorial Sloan-Kettering Cancer Center and Johns Hopkins University School of Medicine, Dr. Goldsmith specifically referred to the use of radionuclides to treat metastatic bone pain.

“The goals of using radionuclides to treat bone pain in cancer patients are to decrease the level of pain, decrease the use of narcotics, prevent new pain, and possibly reduce the rate of tumor progression,” Dr. Goldsmith said. “Although these interventions cannot stop disease progression, these goals are worthwhile, since improvements in the quality of life are critical to patients with advancing disease,” he added.

Several bone-seeking radiopharma-ceuticals are available, and all result in similar levels of pain relief, Dr. Goldsmith said, regardless of the specific half-life or energy level of the isotope used. Moreover, he noted, these agents are all reasonably safe as long as patients have adequate levels of platelets (greater than 60,000/L) and white cells (greater than 3.5 × 10⁹/L).

“Physicians should adjust the dose used to each patient, keeping in mind each patient’s size, weight, and level of disease,” he said.

Radionuclides currently available in the United States for alleviating bone pain are phosphorus-32 orthophosphate , strontium-89 chloride (Metastron), and samarium-153 (Quadramet). Agents under investigation include rhenium-186 HEDP and tin-113m DTPA.

Because these agents preferentially localize to the bone immediately surrounding a tumor, there is limited radiation to uninvolved surrounding tissue, Dr. Goldsmith said.

Response Rates of 75% to 90%

In one study of strontium-89 in 89 patients with bone metastases, approximately 75% of patients responded to treatment; 90% of the patients with minimal bone involvement had clinically significant pain palliation, he said. A study at Memorial Sloan-Kettering Cancer Center of more than 100 patients yielded comparable results; only about 10% to 20% of patients failed to respond to strontium-89 therapy.

Although single-agent radionuclide therapy is beneficial, Dr. Goldsmith also described impressive data collected from patients treated with strontium-89 and external beam radiation. In this study, 126 patients were randomized to receive a therapeutic dose of strontium-89 or a placebo nonradioactive dose following external beam radiation for a single painful metastatic site.

“Not only did all quality of life parameters improve to a greater degree in the strontium-89-treated patients, but the median time to recurrent pain onset in this group was 35 weeks, compared with 23 weeks in those given only external beam radiation,” he said. The onset of pain relief was within 2 weeks of the strontium-89 injection, with significant relief attained by about 80% of patients.

These encouraging results suggest that there may be an antitumor effect of radionuclide therapy, however transient, Dr. Goldsmith said.

“Although there is no evidence for increasing survival time, there is an emerging role for these agents as an adjuvant treatment, particularly since new symptoms can be delayed,” he concluded. “Regardless of the radionuclide chosen, the data indicate that these agents are effective in alleviating pain and improving quality of life for cancer patients.”