Overall survival in non-small cell lung cancer—what is clinically meaningful?

The development of molecularly targeted therapies [tyrosine kinase inhibitors (TKIs) and monoclonal antibodies] has significantly improved outcomes for patients with advanced or metastatic non-small cell lung cancer (NSCLC) resulting in improved progression-free survival (PFS), overall survival (OS) and quality of life (QoL). In addition, targeting the immune axis (CTLA-4, PD-1/PD-L1) has also shown promising results. Major goals of almost all clinical trials based on histology and molecular markers for NSCLC patients are improvements of OS and QoL. However, in the majority of these trials only small incremental improvements in OS were seen. Food and Drug Administration (FDA) and other health authorities have recommended to consider OS to be the standard clinical benefit endpoint that should be used to establish the efficacy of a treatment for NSCLC patients, however, the question remains what is clinically meaningful and how can this outcome be measured. According to suggestions of the American Society of Clinical Oncology (ASCO) Cancer Research Committee a relative improvement in median OS of at least 20% (3–4 months) is regarded to define a clinically meaningful improvement in outcome of NSCLC patients. However, this should not diminish PFS as a valid endpoint since a PFS improvement can also result in a meaningful palliation (e.g., painful bone metastases). Other factors (e.g., QoL) may also be involved to measure and to define the clinical importance of a given trial result. Using the “Quality-adjusted Time Without Symptoms of Toxicity” (Q-TWiST) analysis method it has been demonstrated that a clinically important and meaningful difference for Q-TWiST is 10–15% of OS in a study. Trials that are designed with less ambitious goals, however, may still be of benefit to individual NSCLC patients if the trial endpoints are met. Since there is no single factor which will make a trial clinically meaningful, these recommendations, however, are not intended to set standards for regulatory approval or insurance coverage but rather to encourage patients and investigators to demand more from clinical trials.