Combination of selenium-containing compounds with cytostatics

A method of producing a synergistic cytotoxic effect on a cancer cell in a patient being treated for cancer, comprising contacting the cell with a cytostatic agent or a mixture of cytostatic agents that inhibits mitosis and simultaneously, separately or sequentially contacting the cell with at least one salt of SeO2, by administering to the patient at least one salt of SeO2 in a concentration of 0.1 mg/kg body weight of the patient to 1.25 mg/kg body weight of the patient, and the cytostatic agent in a concentration of 2 mg/m2 body surface of the patient to 240 g/m2 body surface of the patient, or by administering to the patient at least one salt of SeO2 in a concentration of 0.1 mg/kg body weight of the patient to 0.3 mg/kg body weight of the patient, and the cytostatic agent in a concentration of 20 mg/m2 body surface of the patient to 1000 mg/m2 body surface of the patient, whereupon the synergistic cytotoxic effect of the cytostatic agent or the mixture of cytostatic agents and at least one salt of SeO2 on the cell is produced wherein the cancer cell is sensitive to the cytostatic agent and the salt of SeO2.