Non-Small Cell Lung Cancer Symptom Assessment Questionnaire (NSCLC-SAQ): Measurement Properties and Estimated Clinically Meaningful Thresholds From a Phase 3 Study

INTRODUCTION: The NSCLC Symptom Assessment Questionnaire (NSCLC-SAQ) was developed to assess NSCLC symptom severity in accordance with Food and Drug Administration evidentiary expectations leading to Food and Drug Administration qualification in 2018. This study evaluated the NSCLC-SAQ’s measurement properties within a clinical trial. METHODS: The KEYNOTE-598 phase 3 study of participants with stage IV metastatic NSCLC with programmed death-ligand 1 tumor proportion score greater than or equal to 50% was used to assess the NSCLC-SAQ’s reliability, construct validity, responsiveness, and estimate clinically meaningful within-person change. Other patient-reported outcome measures included patient global impression items of severity and change in lung cancer symptoms, and the European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire core 30 and lung cancer module, LC13. RESULTS: Participants (N = 560) were mostly men (70%), had a mean age of 64 years, and had Eastern Cooperative Oncology Group performance status of 1 (64%) or 0 (36%). Internal consistency at baseline (Cronbach’s α = 0.74) and test-retest reliability after 3 weeks (intraclass correlation coefficient = 0.79) were satisfactory. NSCLC-SAQ items, domains, and total score correlated moderately to highly with patient-reported outcome measures capturing similar content, and the total score differentiated among patient global impression of severity groups (p < 0.001). The total score detected improvement over time and the estimated clinically meaningful within-person change threshold for improvement ranged from three to five points on the 0 to 20 scale. Few participants exhibited symptom worsening (n = 38), limiting inferences in this group. CONCLUSIONS: The NSCLC-SAQ was found to be reliable, valid, responsive, and interpretable for assessing symptom improvement in NSCLC. Further evaluation is recommended in trial participants whose symptoms worsen over time.