Among the subspecialties of internal medicine, medical oncology may have had the greatest impact in changing the practice of medicine in the past four decades, as curative treatments have been identified for a number of previously fatal malignancies such as testicular cancer, lymphomas, and leukemia. New drugs have entered clinical use for disease presentations previously either untreatable or amenable to only local means of therapy, such as surgery and irradiation. | -retinoic acid induces a remission in drug-refractory disease and does so without the period of marrow hypoplasia characteristic of cytotoxic drugs. Hormonal agents, planar-polar chemicals, and various retinoids and vitamin D analogs are being tested as differentiation drugs in established cancer and in preventing progression of premalignant disease. As genetic testing becomes increasingly able to identify individuals at high risk of developing cancer, the emphasis in cancer drug development will inevitably shift to the discovery of preventive or differentiating agents. The discovery of the important role of angiogenesis in allowing malignant cells to establish a generous blood supply also has led to current trials of inhibitors of endothelial cell proliferation, including low doses of cytotoxic agents as well as experimental drugs such as monoclonal antibodies to endothelial growth factors and their receptors and low-molecular-weight inhibitors of the receptors, and antiangiogenic peptides such as
