Prediction of response to cancer chemotherapy.

Cytotoxic chemotherapy plays a key role in the treatment of carcinoma for thousands of patients annually who either present with metastatic disease or relapse after surgical excision of apparently localised disease. Unfortunately, there is such a wide range of responsiveness to drug therapy within individual tumour types that response of an individual patient's tumour to cytotoxic therapy cannot be accurately predicted. Intensive efforts to increase the accuracy of selection of effective chemotherapy have recently culminated in an in vitro system which employs soft agar and standard laboratory tissue culture techniques to predict drug sensitivity and resistance for an individual patient's tumour with reasonable accuracy. Research in this system is being actively pursued at several centres and further modifications and refinements may well make cancer chemotherapy more precise than previously possible. This review surveys methods of studying in vitro drug sensitivity which have been tested and for which clinical correlations are available. The technique and results of the more recently developed human tumour stem cell assay and the potential applications of this system are also discussed.