Millions of years were required for evolution to tune the human immune system to its present state, so it should not be surprising that a few more years may be required before we know whether human intervention has been successful in making the immune system more efficient at recognizing and eliminating cancer.

While the science underlying specific approaches focusing on particular tumor antigens is coming of age (see BioCentury, April 27), non-specific approaches are further along in the clinic and may provide the first look at the efficacy of immune stimulation.