The value of a symptom cluster of fatigue, dyspnea, and cough in predicting clinical outcomes in lung cancer survivors

Context: Aggregates of concurrent symptoms, known as symptom clusters (SxCls), are reported to have prognostic capabilities beyond that of single symptom alone. A SxCl of fatigue, dyspnea, and cough has been delineated in a number of lung cancer cohorts. Objectives: The objective of this study was to characterize this SxCl's predictive value for important clinical outcomes relative to that of its component symptoms. Methods: Analysis of an eight-year prospective cohort study that assessed 2405 patients with LC for self-reported symptom burden, employment status, and physical activity with the Baecke questionnaire, and overall quality of life (QoL) was undertaken using nested Cox and generalized linear multilevel mixed models. Models were adjusted for longitudinally assessed demographics, cancer progression and tobacco use, and cancer progression. Results: The SxCl, as well as its individual symptoms and symptom pairs, were all negatively associated with survival in Cox models of Years 1-3 after diagnosis. Only in Year 3 did the SxCl prognosticate survival (and then marginally) better than single symptoms or symptom pairs; fatigue was strongly associated (P ≤ 0.0005) with survival at all time points. The SxCl was not predictive of participants' employment status, physical activity, or QoL, whereas the presence of fatigue, dyspnea, or their combination was strongly associated with these outcomes. Conclusion: Fatigue and dyspnea are strongly associated with poor clinical outcomes in LC survivors; however, a SxCl that includes fatigue, dyspnea, and cough as part as its components does not appear to significantly improve their predictive capability.