Importance and relevance of pulmonary symptoms among patients receiving second- and third-line treatment for advanced non-small-cell lung cancer: Support for the content validity of the 4-item Pulmonary Symptom Index

We assessed the content validity of the 4-item Pulmonary Symptom Index (PSI) through interviews with 20 patients with advanced nonsmall-cell lung cancer (NSCLC) and evaluated the PSI's scalability using existing PSI data from 912 patients. The PSI captures the most important symptoms reported by patients with NSCLC and provides a clinically useful measure of the benefits of lung cancer therapies. Background: In advanced non-small-cell lung cancer (NSCLC), reducing symptoms can be a meaningful treatment outcome. This study characterizes the pulmonary symptoms of patients receiving second- and third-line systemic therapies for NSCLC and assesses the content validity of the 4-item Pulmonary Symptom Index (PSI) of the Functional Assessment of Cancer Therapy - Lung (FACT-L). Methods: Twenty patients with advanced NSCLC undergoing second- and third-line treatment ("qualitative sample") completed semistructured interviews regarding their NSCLC symptoms and the importance of pulmonary symptoms. Results were mapped to the PSI. In addition, existing PSI data from 912 patients with cancer ("validation sample") was analyzed to evaluate the scalability of the 4 PSI items. Results: In the qualitative sample, mean age was 62 years (range 30-79 years); 80% had nonsquamous histologic type, and 25% had comorbid chronic obstructive pulmonary disease (COPD). A core set of pulmonary symptoms emerged in the data - shortness of breath, cough, and chest tightness. These mapped to 3 PSI items. A quarter of the patients reported an absence of pulmonary symptoms, which supports the inclusion of the final PSI item, "breathing is easy." In the validation sample, for the shortness of breath/breathing ease item pair, weighted kappa representing chance-adjusted agreement ranged from 0.39 to 0.54 and percent agreement from 44% to 49% (both considered moderate), supporting a distinct contribution of each item. Conclusion: The PSI captures the most important and relevant symptoms reported by patients with NSCLC receiving second- and third-line treatment. Our results suggest that the PSI may provide a clinically useful method to measure patient benefit from lung cancer therapies.