Biologicals and biological response modifiers: fourth modality of cancer treatment.

Considerable progress has been made in the last 5 years toward the development of specific biological approaches to the treatment of cancer. The techniques of genetic engineering, mass cell culture, and improved techniques in protein and nucleic acid sequencing and synthesis have made available biologicals as specific, highly purified molecules that can be used in cancer therapy. While extensive clinical trials are needed to demonstrate that biologicals and biological response modifiers can provide a survival advantage for patients with cancer, the preliminary data indicate that these approaches can be useful in inducing responses in patients with clinically apparent disease. Further studies with these approaches in conjunction with surgery, radiotherapy, and chemotherapy should be helpful in definitively establishing biologicals and biological response modifiers as the fourth modality of cancer treatment.