The QLQ-C30 and its modules have been designed to evaluate change of HRQOL in clinical trials setting. Therefore, the scores are mainly used in a comparative setting such as:

  • comparing different patient groups at a given time point
  • comparing changes within one group over time
  • comparing changes over time between different patient groups.

When comparing scores, it is important keep in mind that statistically significant differences do not necessarily imply clinically relevant differences or changes and vice versa.

A minimum important difference (MID) of 5 to 10 points, as defined by Osoba et al (J Clin Oncol 1998), is generally recommended for interpreting group differences and changes in the EORTC QLQ-C30 scale scores as clinically meaningful. The rationale for using MIDs of 5 to 10 points has been supported in several papers, specific for the QLQ-C30. Of note is the paper by King et al (Qual Res 1996) where known-group comparisons were used to establish a between group difference.

However, note that more recent guidelines have highlighted that the 5 to 10 points rule may be too simplistic in that it does not differentiate between the QLQ-C30 scales, between directions of change (improvement vs deterioration), and may not be achievable in all settings (Cocks et al J; Clin Oncol 2010, and Cocks et al; EJC 2012). Below are some additional useful references that should also be consulted when selecting clinically meaningful thresholds for group differences and changes across the different QLQ-C30 scales, for improving and deteriorating scores, and in different disease settings.

  • Musoro JZ, Coens C, Sprangers et al. EORTC Melanoma, Breast, Head and Neck, Genito-urinary, Gynecological, Gastro-intestinal, Brain, Lung and Quality of Life Groups. Minimally important differences for interpreting EORTC QLQ-C30 change scores over time: A synthesis across 21 clinical trials involving nine different cancer types. Eur J Cancer. 2023 Jul;188:171-182. doi: 10.1016/j.ejca.2023.04.027. Epub 2023 May 7. PMID: 37257278.
  • Cocks K, et al. Evidence-Based Guidelines for Determination of Sample Size and Interpretation of the European Organisation for the Research and Treatment of Cancer Quality of Life Questionnaire Core 30. J Clin Oncol 2010; 29(1): 89–96.
  • Cocks K, et al. Evidence-based guidelines for interpreting change scores for the European Organisation for the Research and Treatment of Cancer Quality of Life Questionnaire Core 30. European Journal of Cancer (2012) 48, 1713– 1721.
  • Maringwa JT, et al. on behalf of the EORTC PROBE project and the Lung Cancer Group. Minimal important differences for interpreting health-related quality of life scores from the EORTC QLQ-C30 in lung cancer patients participating in randomized controlled trials. Support Care Cancer. 2011 Nov; 19(11):1753-60.
  • Maringwa J, et al. Minimal Clinically Meaningful Differences for the EORTC QLQ-C30 and EORTC QLQ-BN20 Scales in Brain Cancer Patients. Ann Oncol. 2011 Sep; 22(9):2107-12.