SR-89 CHLORIDE (METASTRON) FOR PALLIATIVE TREATMENT OF BONY METASTASES - THE UNIVERSITY-OF-MINNESOTA EXPERIENCE

Strontium-89 chloride (Metastron) is an FDA-approved treatment for pal liation of cancer pain. We evaluated blood count changes and pain reli ef in 28 patients with widespread painful bony metastasis treated with strontium-89 at the University of Minnesota Hospital and Clinics. Eig hteen patients had prostate cancer (all hormone-refractory cancer), se ven patients had breast cancer, and three patients had lung cancer, al l previously treated with either radiation, chemotherapy, or a combina tion of the two. Serial blood counts were performed weekly up to 8 wee ks and at 12 weeks after administering Metastron. Pain scale and blood values were monitored simultaneously. The mean baselines of hemoglobi n (Hgb), white blood count (WBC), and platelets (Pits) were 11.4, 5900 , and 258,000, respectively. The mean dose of Metastron was 3 mCi (ran ge 2.2-4.4). The median time (range) to nadir was about 6 weeks. The p ercentage reductions relative to baseline were 32% (range 0-72%) for W BC; 14% (range 0-50%) for Hgb; 15% (range 0-47%) for the red blood cel l (RBC) count; and 40% (range 0-85%) for Pits. We did not find a close relationship among the baseline blood count, reduction of subsequent blood counts, or previously irradiated active bone marrow volume. The median time of survival was 23 weeks (range 2-66 weeks). At 12 weeks, 29% of patients had moderate to dramatic improvement of pain, 32% had some relief of pain, and 50% had no improvement in pain. Thirty-two pe rcent of the treated patients required additional palliative external beam radiation to their bony lesions within the study period. Our resu lts show that Metastron for palliation for bony metastases should be u sed with caution because of moderate to severe bone marrow toxicity, e specially in platelets, associated with its use. Careful evaluation of patients given Metastron is needed to assess accurately its full bene fit.