Platelets and malignancy. Rationale and experimental design for the VA Cooperative Study of RA-233 in the treatment of cancer.

Considerable evidence has accumulated in recent years which implicates blood coagulation reactions in the growth and spread of malignancy. In particular, platelets may accumulate on embolic tumor cells and facilitate their adhesion to the endothelium at distant sites perhaps by enhancing blood coagulation reactions. Alternatively, platelets may promote tumor cell proliferation by contributing a growth-promoting factor or through interactions mediated by prostaglandins. Inhibition of tumor growth and spread by platelet-inhibitory drugs has been demonstrated in several experimental tumor systems. Preliminary data suggest that similar effects may be seen in human malignancy. The purpose of this paper is to review relevant literature which provides the rationale for therapeutic trials of platelet-inhibitory drugs in human malignancy and to describe the experimental design for a trial involving one such drug, RA-233, in a recently established VA Cooperative Study.