Evaluation of radiotoxicity after strontium-89 therapy for bone metastases using the micronucleus assay.

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It is unexpected that strontium-89 (Sr^<89>), as a new investigational drug, is not clinically available in our hospital until now. We can not evaluate the cytological radiation damage to lymphocytes after strontium-89 (Sr^<89>) therapy, which have a role in palliating metastatic bone diseases, using the cytokinesis-blocked micronucleus assay (CBMA) in the present study. Therefore, using CBMA we evaluated the degree of cytological radiation damage to lymphocytes in esophageal cancer patients with radiation therapy (RT) accompanying with external irradiation consequently for vertebral bones. This RT may be closely correlated to RT for bone metastases. The chromosomal damage to lymphocytes induced by irradiation should result in augmentation of the cells with micronuclei. Methods : We studied 12 patients with esophageal cancer, who were treated with RT. Isolated lymphocytes collected from patients within 1 week after therapy were harvested and treated according to the cytokinesis-blocked method of Fenech and Morley. Micronucleus number of lymphocytes micronuclei per 500 binucleated cells was scored by visual inspection. As controls, lymphocytes from the same patients before therapy were also studied. In an in vitro study, lymphocytes from eight normal volunteers were exposed with doses varying from 0.5 to 2.0 Gy and studied with the same method. Results : The mean number (mean±SD) of lymphocytes after RT was significantly increased (p<0.05) as compared to control subjects (52±10.7 vs. 8.8±1.8). In an in vitro study, these data fit a nonthreshold, linear dose-response function.Conclusions : The relatively low frequency of lymphocyte micronuclei induced by this RT in vivo supported the contention that short-term non-stochastic damage with RT in patients with painful bone metastases may be minimal.