PURPOSE: In this study, we investigated the clinical and laboratory factors that may enhance (89)Sr uptake to strengthen its tumoricidal effect. METHODS: We enrolled 21 patients with multiple bone metastases (n = 23) from breast cancer and classified them into 2 groups according to their zoledronic acid (ZOL) treatment history. (89)Sr imaging with bremsstrahlung was performed 2 to 6 weeks after administration and (89)Sr index was measured using combined imaging with bone scintigraphy. We compared the Sr index with the levels of alkaline phosphatase, bone-specific alkaline phosphatase, serum cross-linked N-telopeptides, carboxy-terminal telopeptide of type 1 collagen, C-reactive protein, calcium, and hemoglobin on administration and evaluated the differences among the groups. RESULTS: The (89)Sr index ranged from 0.01 to 2.0 and was significantly correlated with C-reactive protein and alkaline phosphatase and moderately correlated with carboxy-terminal telopeptide of type 1 collagen, serum cross-linked N-telopeptides, and bone-specific alkaline phosphatase. The (89)Sr index was not significantly correlated with calcium or hemoglobin. The group with less than 1 year of ZOL treatment demonstrated a mean (SD) (89)Sr index of 1.11 (0.59), and the group with 1 or more years of ZOL treatment showed a mean (89)Sr index of 0.36 (0.26). The Wilcoxon signed-rank test demonstrated a significant difference between the 2 groups (P < 0.001). CONCLUSIONS: (89)Sr accumulation seemed to be associated with bone turnover, in particular bone resorption, and vascularization due to inflammation or tumor growth. Long-term ZOL treatment may reduce bone resorption and vascularization. To enhance the tumoricidal effect and palliation of bone pain by (89)Sr, combined therapy must be established.
PURPOSE: In this study, we investigated the clinical and laboratory factors that may enhance (89)Sr uptake to strengthen its tumoricidal effect. METHODS: We enrolled 21 patients with multiple bone metastases (n = 23) from breast cancer and classified them into 2 groups according to their zoledronic acid (ZOL) treatment history. (89)Sr imaging with bremsstrahlung was performed 2 to 6 weeks after administration and (89)Sr index was measured using combined imaging with bone scintigraphy. We compared the Sr index with the levels of alkaline phosphatase, bone-specific alkaline phosphatase, serum cross-linked N-telopeptides, carboxy-terminal telopeptide of type 1 collagen, C-reactive protein, calcium, and hemoglobin on administration and evaluated the differences among the groups. RESULTS: The (89)Sr index ranged from 0.01 to 2.0 and was significantly correlated with C-reactive protein and alkaline phosphatase and moderately correlated with carboxy-terminal telopeptide of type 1 collagen, serum cross-linked N-telopeptides, and bone-specific alkaline phosphatase. The (89)Sr index was not significantly correlated with calcium or hemoglobin. The group with less than 1 year of ZOL treatment demonstrated a mean (SD) (89)Sr index of 1.11 (0.59), and the group with 1 or more years of ZOL treatment showed a mean (89)Sr index of 0.36 (0.26). The Wilcoxon signed-rank test demonstrated a significant difference between the 2 groups (P < 0.001). CONCLUSIONS: (89)Sr accumulation seemed to be associated with bone turnover, in particular bone resorption, and vascularization due to inflammation or tumor growth. Long-term ZOL treatment may reduce bone resorption and vascularization. To enhance the tumoricidal effect and palliation of bone pain by (89)Sr, combined therapy must be established.