Researchers need to collect information (called outcomes or endpoints) to help them decide which treatment is most effective and safest.
In a phase 2 trial, the first outcome that researchers look for is how effective the treatment has been in treating the cancer. In solid tumours (not lymphomas, leukaemia and myeloma), if the cancer has stopped growing, shrunk or disappeared it’s known as a response. You may hear your doctors use different phrases to describe your response to treatment, such as a complete or partial response or stable disease.
A complete response is defined as the disappearance of all of the detectable cancer for at least four weeks. Clearly this is a very good result, but a complete response doesn’t always mean a cure. It takes several years with no sign of the cancer returning (recurrence) before it can be thought of as cured.
A partial response is a decrease in cancer size by at least 30% for at least four weeks, without any signs of growth elsewhere in the body.
Stable disease is when the cancer has shrunk in size, but by less than 30%, and there are no signs of growth elsewhere in the body.
Some trials look at longer-term outcomes of treatment. In a phase 3 trial, researchers are often looking at how long people live after the treatment (survival). Doctors and researchers monitor whether more people are cured, or live longer, with the new treatment.