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Calcium antagonist radioprotectors do not reduce radiotherapeutic efficacy in three human tumor xenografts
1Department of Research, University Hospitals, Basel, Switzerland.
Aim:
Calcium antagonists, which protect normal tissue as exemplified by bone marrow cells from radiation injury, were evaluated for radioprotection of tumor cells.
Materials And Methods:
One Ewing's sarcoma and 2 colon carcinomas were grown as xenografts in immunosuppressed mice. The mice were treated with diltiazem, nifedipine, nimodipine and nitrendipine. The effect of whole body gamma-radiation on the growth of the subcutaneously implanted tumors was assessed.
Results:
Growth delay or regression of the tumors in mice treated with the calcium antagonists prior to irradiation was not reduced as compared to only irradiated controls.
Conclusion:
The tested calcium antagonists, which are well tolerated and protect mice from death after lethal radiation, did not prevent the radiotherapeutic effect on 3 human tumors. This points to the possibility of differential radioprotection and thus to improve the therapeutic ratio in cancer radiotherapy.
