HEY, IF IT MAKES YOU FEEL BETTER: The Placebo Effect in Action: Research and Everyday Life. “The placebo effect occurs more often with subjective symptoms, such as pain, rather than objective medical evidence, such as a tumor identified on a computed tomography (CT) scan. In other words, a placebo treatment may help improve your pain, but it is not going to kill cancer cells the way actual chemotherapy drugs do.” That said, killing actual cancer cells would be good.