The concept and use of placebo and nocebo in oncology

Placebo and nocebo effects recognised through all of the history of medicine, and these effects can be found also in the field of oncology research and clinical practice. Placebo effect are more than the effects of an inert substance. Placebo benefits the health status because of the person’s belief and nocebo worsens the health status of the patient. Several psychological mechanisms are involved in placebo/nocebo effects; expectation, learning processes (classical conditioning and observational learning), reinforced expectations, personality traits of the patient and the health care provider. At the same time placebo effects rely on neurobiologic mechanism (neurotransmitters like dopamine, cholecystokinin, opioids and activation of specific brain areas). The use of placebo is an important methodological tool in oncological research and drug development. Inert substance can be associated with positive (placebo) and negative (nocebo) adverse event profiles also can modify the measured therapeutic effects in randomized clinical trials.