Background: The underpinning conceptual model for the Lung Cancer Symptom Scale (LCSS), an instrument used to assess health-related quality of life in patients with lung cancer, has been described elsewhere. The patient-rated scale of the LCSS was modified slightly for patients with mesothelioma (LCSS-Meso), because no other mesothelioma-specific instrument was available.
Methods: In the current methodologic study, the authors tested the conceptual model for the LCSS-Meso. Chemotherapy-naive patients with unresectable malignant pleural mesothelioma who were participating in two clinical trials of pemetrexed (ALIMTA; Eli Lilly, Indianapolis, IN) completed the scale twice before the start of therapy and once weekly during the trials. Three time points were analyzed: baseline, Day 40, and Day 82. Poisson regression was used to determine the contribution of predictive factors (i.e., symptoms) to the summary items (symptom distress, activity level, and global quality of life).
Results: The model was tested in 495 patients who had malignant pleural mesothelioma. More than 85% of patients reported pain, dyspnea, fatigue, and appetite loss. Pain, dyspnea, and fatigue were significant and stable predictors for all summary items; however, pain had a significant effect on global quality of life only through Day 40. Appetite loss was a significant and stable predictor of activity level and global quality of life. The explained variance for the model was 39-55%.
Conclusions: Further support for the content validity of the LCSS-Meso was obtained, as nearly all patients validated that the symptoms described in the scale captured their disease experience. The only exception was the hemoptysis item, which was removed based on the current large normative data set. Support for the construct validity of the LCSS-Meso also was obtained. For both mesothelioma and lung cancer, the majority of factors within the LCSS model are relevant and have the expected amount of variability. These findings support the use of the LCSS as a sensitive instrument for serial measurement during clinical trials involving patients with lung malignancies.