Challenges in defining and identifying patients with non-small cell lung cancer and poor performance status.

Performance status (PS), a subjective measure of the functional status of a patient with cancer and his or her ability to perform normal activities, is influenced both by tumor-related and by comorbidity-related factors. It is a reliable independent prognostic indicator for survival in patients with advanced non-small cell lung cancer. Patients with a poor PS (PS2) constitute up to 30% to 40% of the population of patients with advanced non-small cell lung cancer, yet they are underrepresented in clinical trials. These patients are heterogeneous, which makes it challenging to use their PS scores alone to guide their therapy. A greater understanding of PS scores and the factors that affect them can be gained through PS2-specific clinical trials, which can lead to the development of better PS instruments to aid in making therapeutic decisions.