Validation of the functional assessment of cancer therapy--lung symptom index-12 (FLSI-12).

We tested the reliability and validity of a brief symptom index for use with patients in the advanced stages of lung cancer. The Functional Assessment of Cancer Therapy--Lung Symptom Index-12 (FLSI-12) is a brief self-report measure that combines seven items addressing symptoms common in advanced-stage lung cancer with five symptoms or concerns that are relevant to most people with advanced-stage cancer. The index was administered prospectively to 92 advanced-stage lung cancer patients beginning at the initiation of chemotherapy and for 12 consecutive weeks. Reliability, convergent and concurrent validities, and responsiveness to change were determined and a minimally important difference (MID) was estimated. The index had good internal consistency (all Cronbach's alpha's>0.70), moderate to high item-to-total correlations (93% rho's> or =0.30), and correlated highly with a measure of overall quality of life (rho's> or =0.50). Baseline scores differentiated patients with better versus worse clinical features (p's<.05). Prospective changes in index scores were sensitive to changes in performance status ratings (p's<.05). An MID of 3-4 points was estimated by combining guideline-, distribution-, and anchor-based methods. The results show that the FLSI-12 is a psychometrically sound measure and support its use as an endpoint in clinical trials of advanced-stage lung cancer.