A review of clinical trials shows that placebos may relieve symptoms like pain, in cancer, but do not lead to a tumour response.

People often do respond in some way to being given a placebo, even though the 'dummy' pill or treatment cannot actually have a pharmacological effect, because it has no active ingredient. Researchers in France and Canada have surveyed a large number of clinical trials involving cancer patients, in an attempt to assess what effect a placebo really has.

They found that improvements in pain and appetite did sometimes occur. But the placebos had no effect on quality of life, weight gain or, importantly, the tumour itself. The effects of placebo could be equivalent to that of a high quality of supportive care. The researchers conclude that in a clinical trial, any improvement in tumour response or outcome is likely to be due to the effects of the active treatment - usually a new drug - rather than to the placebo.

Source

Journal of the National Cancer Institute 1st January 2003