Table 1. Development of the QLQ-LC29: phase 1 to 4.

Phase	Method	Results
Phase 1: Generation of issues	Literature review, review of questionnaires in the field, interviews with patients and health care providers	QLQ-LC13 was used in 240 clinical trials, among them 109 RCTs. 92/109 (84%) of the RCTs addressed QoL in the abstract. In none of the studies major problems with the use of the QLQ-LC13 were reported
		In addition, 25 questionnaires relating to respiratory diseases were reviewed
		The literature review and the review of existing questionnaires yielded a total of 110 QoL issues to be considered in the context of lung cancer
		108 patients and 103 health care providers from nine countries evaluated this list of issues regarding relevance and whether each of the issues should be included in the questionnaire
		The analyses found 53 issues as relevant
Phase 2: Item generation and construction of a provisional questionnaire	Using the EORTC item library, questionnaires items were formulated that were compatible with the standard response scale (1= not at all, 2= a little, 3= quite a bit, 4= very much)	After correcting for overlap/redundancy (also with the QLQ-C30), the provisional module contained 48 items
		12 out of the 13 original QLQ-LC13 items were retained
		The 48-item questionnaire was translated into the following (with English as the source language): German, Greek, Hebrew, Italian, Mandarin (Taiwan Chinese), Norwegian, Polish, and Spanish
Phase 3: International study to assess comprehensibility, acceptance, and relevance	200 patients from nine regions (Cyprus, Germany, Israel, Italy, Norway, Spain, Poland, Taiwan, UK) filled in the QLQ-C30 and the provisional updated lung cancer module. They rated each item regarding comprehensibility, acceptance, and relevance	29 of the 48 items met the pre-specified threshold criteria
	Item selection criteria were specified in advance which took into account patients’ ratings as well as each item’s distribution properties, such as mean, range, floor/ceiling effects, prevalence of 3 and 4 responses, and missing responses	12 out of the 13 original QLQ-LC13 items were retained, and newly added items addressed side-effects of targeted therapy, immunotherapy, surgery, as well as fear of progression
Phase 4: International study to assess the psychometric properties of the QLQ-LC29	523 patients from 12 regions (Belgium, Cyprus, Germany, Greece, Israel, Italy, Jordan, Norway, Spain, Poland, Taiwan, UK) filled in the QLQ-C30 and the QLQ-LC29. 195 patients filled in the questionnaire at a second assessment point	Confirmatory factor analyses is best compatible with a scale structure comprising five multi-item scales (coughing, shortness of breath, dyspnea, fear of progression, hair problems, surgery-related symptoms) and 15 single items
	The goal was to determine the scale structure, and to assess reliability, validity (known-group differences) and responsiveness to change	Internal consistencies of all multi-item scales ranged between 0.73 and 0.86, and test-retest reliabilities ranged between 0.82 and 0.97. Four of the 5 multi-item scales yielded known group differences when patients with lower vs. higher Karnofsky Performance Status were contrasted (P<0.01). Three of the 5 multi-item scales showed responsiveness to change over time (P<0.05), so did 9 out of 15 single symptoms

QLQ, Quality of Life Questionnaire; RCT, randomized controlled trial; EORTC, European Organization for Research and Treatment of Cancer.