A method for treatment of a tumor including administering to a patient in need thereof a pharmaceutical preparation including a combination of a deoxynucleoside and a nucleoside. The deoxynucleoside is selected from deoxyadenosine, deoxyguanosine, deoxycytidine, thymidine, or a mixture thereof. The nucleoside is selected from adenosine, guanosine, cytidine, uridine, deoxyadenosine, deoxyguanosine, deoxycytidine, thymidine, or a mixture thereof.