Prospective Minimal Important Difference (pMID) Project: Interpreting changes in EORTC QLQ-C30 scores by anchoring to patients’ rating of change – Phase I

The concept of minimally important difference (MID) enables the interpretation of changes in HRQOL scores over time in terms of clinical meaningfulness. A key method for estimating MIDs is the anchor-based approach which quantifies changes in HRQOL scores by linking particular HRQOL domains either to known variables, which have clinical relevance, or to patient-derived/physician-derived ratings of clinically relevant change in the particular domain. Osoba et al established a patient-centered approach for establishing MIDs for the EORTC QLQ-C30 by using a change questionnaire (CQ) called subjective significance questionnaire (SSQ) as anchor; which asked patients about their perceived changes over time. However, this study was limited to patients with either breast or small-cell lung cancer, included only four of the fifteen QLQ-C30 scales, and did not differentiate between direction of change (improvement vs deterioration). In addition, there is lack of standardised methodology on development and validation of such CQs. The aim of this project, thus, is to:

– perform a systematic review to report on current practices for developing CQs in oncology and their application in establishing anchor-based MIDs, and appraise the properties of reliable CQs to refine and perfectly validate our new CQ,
– prospectively estimate MIDs for all the EORTC QLQC30 scales by anchoring to the new well-validated CQ.

• The screening part of the systematic review is done.
• Data extraction and full-text review is currently undergoing.
• An abstract on initial results on the systematic review will be submitted to ISOQOL 2022

The project is currently in the systematic review phase; full-text review and data extraction are ongoing.
We plan to:
• Finalise the systematic review by June 2022 and start developing the study protocol
• Release of the protocol is planned for September 2022

Patient reported outcomes (PRO) such as health-related quality of life (HRQOL) are increasingly being used in oncology as a way of including the patient’ voice to help assess therapeutic intervention (e.g. a new treatment). To improve interpretation of changes in HRQOL scores, one must understand the amount of change that a patient will perceive as important. Researchers have developed the concept of minimal important difference (MID) to measure the smallest difference in HRQOL scores that most patients perceive as a relevant change. A well-recognised approach for establishing MIDs is the anchor-based method where changes in HRQoL scores are explained using an external variable (anchor) for which change is more understood. As a more patient-centred approach, we aim to establish MIDs for all EORTC QLQ-C30 scales by using patient-based anchor; change questionnaire (CQ), which allows patients to rate themselves on how much they have changed over a certain period.
Our results will supplement previously published MID guidelines and contribute to building more robust and practical interpretational guidelines for the EORTC QLQ-C30.