Definitions and measurements of adherence vary widely; this prevents comparisons being made between studies and populations. There is little information on the adherence to palliative treatment of patients with cancer, and it covers only treatments for relief of pain. The available information reports adherence rates ranging from 24.7% to 88.9%. A general programme of palliative care must include the management of adherence in order to improve the effectiveness of the interventions and ensure an acceptable quality of life for this group of patients.

More research on adherence to palliative care is required in the following areas:

- epidemiology of adherence, especially to medicines other than those for pain relief;

- determination of the most appropriate methods and definitions for the measurement of adherence to analgesic medications;

- determining the additional factors that contribute to a patient's level of adherence to all required therapies; and

- studies evaluating interventions to improve adherence to all required therapies.