The current role of cancer chemotherapy

Cancer chemotherapy has developed rapidly over the last twenty years. The majority of patients with cancer die from metastatic disease, so the major therapeutic advance now must be better systemic therapy. From its early beginning in the 1940's with oestrogen therapy for prostatic cancer, nitrogen mustards in the lymphomas, and folic acid antagonists in childhood leukaemia, there are now between thirty and forty active anti-cancer agents in clinical use. The main clinical pharmacological points of the major agents are briefly reviewed, together with their main dose-limiting toxic effects and their activity as single agents. Clinical chemotherapy has developed by the introduction of newer agents from the drug screening programmes and a better understanding of the scheduling to avoid serious toxicity. Although drug-resistance is still a major problem, by combining different active agents there has been a dramatic improvement in survival of patients with selected tumours. More recently, treatment of patients early, before they have gross clinical recurrence, has already shown some benefit in pre-menopausal patients with carcinoma of the breast and in patients with osteosarcoma. The limitations of clinical measurements in monitoring therapy are clear, and a major improvement could well be realised if therapy could be monitored on the basis of quantitative markers. The clinical impact of cancer chemotherapy has already been dramatic in drug-sensitive tumours, but these only contribute a small proportion of the total. Some of the common tumours fall into the group that are relatively drug sensitive where the lives of patients can be prolonged, but there is still a significant fraction of tumours which are insensitive to existing drugs and which will probably require the development of newer agents before chemotherapy can make any impact on the survival of patients with these tumours.