Psychometric Properties of the EORTC QLQ-LC29

Background The EORTC QLQ-C30 assesses quality of life of cancer patients and comprises 30 items that are grouped in five functional scales (physical, role, cognitive, emotional and social), one scale to rate global health and quality of life, three multi-item symptom scales (fatigue, nausea and vomiting, pain) and five single symptom items (dyspnoea, insomnia, appetite loss, constipation and diarrhea), one item assessing perceived financial impact of disease and treatment.

The updated lung cancer module, the QLQ-LC29, is a module to be used in conjunction with the QLQ-C30 for the assessment of specific aspects of quality of life in patients with lung cancer. All items are accompanied by the classic EORTC four-point Likert response scale with the labels 1 "not at all", 2 "a little", 3 "quite a bit", and 4 "very much". The time frame is the past week ("Please indicate the extent to which you have experienced these symptoms or problems during the past week").

Eligibility Patients are eligible for this study if they have a histologically confirmed diagnosis of lung cancer, are able to understand the language of the questionnaire, are mentally fit to complete the questionnaire, and have provided written informed consent.

Sampling matrix Participants will be enrolled in four groups according to their primary therapy: A. Surgery, B. Radiochemotherapy, C. Targeted therapy, D. Immunotherapy. Various combinations of therapies are possible, resulting in a total of eight subgroups: A.1 Surgery alone and/or before any adjuvant therapy, A.2 Surgery (late effects), B.1 Chemotherapy alone, B.2 Radiotherapy alone, B.3 Sequential radiochemotherapy, B.4 Concurrent radiochemotherapy, C.1 Targeted therapy alone, C.2 Targeted therapy in combination with any other therapy, D. Immunotherapy.

Procedure Patients are informed about the goal of the study. After granting informed consent, patients fill in the self-administered paper version of the EORTC QLQ-C30 plus the new lung module QLQ-LC29. Their physicians provide the clinical documentation. A subsample of the patients will fill in the questionnaires at a second time point two to four weeks later.

Sample size According to sample size calculations we will include a total of N = 450 patients, but inflating the recruitment goal is permissible.

Statistical analyses Scale structure will be analysed by confirmatory factor analyses, and backed by classical test theory (convergent/discriminant validity). Reliability will be calculated by means of Cronbach's alpha (internal consistency) and intra-class coefficient (ICC, test-retest reliability). Sensitivity of the module will be assessed by means of known group differences (Karnofsky Performance Status). Responsiveness to change over time will take into account differences between the second and first assessment.

Inclusion criteria

• histologically confirmed diagnosis of lung cancer
• no previous primary or recurrent tumour
• ability to understand the language of the questionnaire
• mental fitness to complete a questionnaire
• 18 years of age or above
• written informed consent.-

Exclusion criteria

• no histologically confirmed diagnosis of lung cancer-
• previous primary or recurrent tumour
• not mentally fit to complete a questionnaire
• not able to understand the language of the questionnaire
• younger than 18
• refusal of informed consent.