A drug based on a metabolite of fenretinide, or N-(4hydroxyphenyl) retinamide (4-HPR), specifically 4-oxo-N-(4-hydroxyphenyl) retinamide (4-oxo-4-HPR), is used in the treatment of different kinds of tumors, in particular in the treatment of ovarian carcinoma, breast tumor and neuroblastoma. The drug is more potent than fenretinide alone, and enhances the effects of fenretinide when administered together with fenretinide.