Meaningful change in cancer-specific quality of life scores: differences between improvement and worsening

There has been increased recent attention to the clinical meaningfulness of group change scores on health-related quality of life (HRQL) questionnaires. It has been assumed that improvements and declines of comparable magnitude have the same meaning or value.

We assessed 308 cancer patients with the Functional Assessment of Cancer Therapy (FACT) and a Global Rating of Change. Patients were classified into five levels of change in HRQL and its dimensions based upon their responses to retrospective ratings of change after 2 months: sizably worse, minimally worse, no change, minimally better, and sizably better. Raw score and standardized score changes on the FACT-G subscales and total score were then compared across different categories of patient-rated change.

The relationship between actual FACT change scores and retrospective ratings of change was modest but usually statistically significant (r: 0.07 to 0.35). Change scores associated with each retrospective rating category were evaluated to determine estimates of meaningful difference. Patients who reported global worsening of HRQL dimensions had considerably larger change scores than those reporting comparable global improvements. Although related to a ceiling effect, this remained true even after removing cases that began near the ceiling of the questionnaire.

Relatively small gains in HRQL have significant value. Comparable declines may be less meaningful, perhaps due to patients' tendency to minimize personal negative evaluations about one's condition. This has important implications for the interpretation of the meaningfulness of change scores in HRQL questionnaires. Factors such as adaptation to disease, response shift, dispositional optimism and the need for signs of clinical improvement may be contributing to the results and should be investigated in future studies.