Long-term survival in small cell lung cancer: the case for a standard definition

Abstract Objectives . This paper investigates whether a particular time point can be recommended as the standard definition for long-term survival (LTS) in small cell lung cancer (SCLC). Design . A review of the literature specifically referring to long-term survival in SCLC in the title. Individual and updated survival data from 2196 patients entered into six Medical Research Council (MRC) SCLC randomised trials to investigate changes in the hazard, or risk of death, over time. Examination of subgroups to identify different hazard patterns. Setting . World-wide literature and patients recruited to SCLC trials conducted by the MRC Lung Cancer Working Party (LCWP). Subjects . Papers accessed through computerised literature and hand searches and 2196 patients from six randomised clinical trials in SCLC conducted by the MRC LCWP. Results . In all, 111 publications were identified by the literature searches. Although the majority defined LTS as 2 years, the definitions ranged from 18 months to greater than 5 years. There thus appears to be no agreed standard definition. The daily hazard was plotted for the large series of patients entered into the MRC LCWP SCLC trials to observe any patterns of change. There was an approximately constant daily hazard of 0.0035 during the first 2 years from randomisation, and following a transitional period, there was a further approximately constant, but smaller, daily hazard of 0.00035 from 3 years onwards. When subgroups of patients were examined this transition to a lower risk was observed in patients with limited disease, but patients with extensive disease remained at a high constant hazard throughout. It is suggested that 3 years should be adopted as the standard definition of LTS in SCLC, and that studies should always report limited and extensive stage patients separately.