Abstract
BackgroundThe EORTC-QLQ-C30 is a widely used health related quality of life (HRQoL) questionnaire in lung cancer patients. Small HRQoL treatment effects are often reported as mean differences (MDs) between treatments, which are rarely justified or understood by patients and clinicians. An alternative approach using odds ratios (OR) for reporting effects is proposed. This may offer advantages including facilitating alignment between patient and clinician understanding of HRQoL effects.MethodsData from six CRUK sponsored randomized controlled lung cancer trials (2 small cell and 4 in non-small cell, in 2909 patients) were used to HRQoL effects. Results from Beta-Binomial (BB) standard mixed effects were compared. Preferences for ORs vs MDs were determined and Time to Deterioration (TD) was also compared.ResultsHRQoL effects using ORs offered coherent interpretations: MDs >0 resulted in ORs >1 and vice versa; effect sizes were classified as ‘Trivial’ if the OR was between 1 ± 0.05 (i.e. 0.95 to 1.05); ‘Small’: for 1 ± 0.1; ‘Medium’: 1 ± 0.2 and ‘Large’: OR <0.8 or >1.20. Small HRQoL effects on the MD scale may translate to important treatment differences on the OR scale: for example, a worsening in symptoms (MD) by 2.6 points (p = 0.1314) would be a 17 % deterioration (p < 0.0001) with an OR. Hence important differences may be missed with MD; conversely, small ORs are unlikely to yield large MDs because methods based on OR model skewed data well. Initial evidence also suggests oncologists prefer ORs over MDs since interpretation is similar to hazard ratios.ConclusionReporting HRQoL benefits as MDs can be misleading. Estimates of HRQoL treatment effects in terms of ORs are preferred over MDs. Future analysis of QLQ-C30 and other HRQoL measures should consider reporting HRQoL treatment effects as ORs.Electronic supplementary materialThe online version of this article (doi:10.1186/s12955-015-0374-6) contains supplementary material, which is available to authorized users.
Highlights
The EORTC-QLQ-C30 is a widely used health related quality of life (HRQoL) questionnaire in lung cancer patients
(iii)‘Study 10’: A phase II trial comparing Gemcitabine/ Carboplatin versus Cisplatin/Etoposide in patients with small cell lung cancer (SCLC) [20]; N = 241. (iv) ‘Study 11’: A phase III trial comparing Gemcitabine/Carboplatin versus Mitomycin/ Ifosfamide /Cisplatin in patients with stage IIIB or IV NSCLC [9]; N = 422 (v)‘Study 12’: A phase III trial comparing Thalidomide combined with chemotherapy versus chemotherapy alone in SCLC patients [21]; N = 724 (vi) Study 14: A phase III trial comparing Thalidomide/ Gemcitabine/Carboplatin versus Gemcitabine/ Carboplatin alone in NSCLC patients [22]; N = 722
An alternative metric to the commonly reported mean differences (MDs) was presented in the form of odds ratios (OR)
Summary
The EORTC-QLQ-C30 is a widely used health related quality of life (HRQoL) questionnaire in lung cancer patients. Small HRQoL treatment effects are often reported as mean differences (MDs) between treatments, which are rarely justified or understood by patients and clinicians. An alternative approach using odds ratios (OR) for reporting effects is proposed. This may offer advantages including facilitating alignment between patient and clinician understanding of HRQoL effects. Health related quality of life (HRQoL) is an important endpoint in cancer trials for several reasons. Where effect sizes are small, HRQoL can ‘add value’ to expensive cancer treatments. For QL and function domains, high scores indicate better HRQoL. For symptom domains (and FI), low scores indicate better HRQoL
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