Small-cell lung cancer: patients included in clinical trials are not representative of the patient population as a whole.

Purpose: To determine the clinical characteristics of the subpopulation of patients not included in clinical trials, their outcome, and the reasons for their ineligibility and non-participation.
Patients and Methods: We studied 57 patients (out of 178 consecutive patients with SCLC), who were not included in any of the three successive clinical trials completed at our center during the study period. We also compared 37 patients excluded from the largest clinical trial to their 73 included counterparts.
Results: Reasons for ineligibility (n = 53) included low Karnofsky index (n = 17), advanced age (n = 12), non-feasible long-term follow-up (n = 12), previous history of cancer (n = 8), contraindication for anthracyclines (n = 5), and other medical reasons (n = 11). Only four eligible patients were not included in the trials. As compared to patients included in the studies, non-included patients had a significantly lower Karnofsky index, were older, presented more frequently with metastatic disease, and had a lower response rate to treatment and a shorter survival. However, exclusion from the trial was not an independent prognostic factor by multivariate analysis.
Conclusions: Selection biases were unlikely in the three trials, based on the high ratio of included/eligible patients. However, the subgroup of patients included in the trials was not representative of the patient population as a whole because of restrictive eligibility criteria. Results from published clinical trials to the overall population should be extrapolated only with caution. We suggest that the proportion and major characteristics of ineligible and non-participating patients be mentioned in any publication of a clinical trial.