e20076 Background: Small cell lung cancer (SCLC) is an aggressive disease currently treated as soon as possible given its rapid doubling time. Evidence for appropriate timing of chemotherapy from diagnosis (TCD) for SCLC is lacking. This study evaluates TCD in SCLC on a national level. Methods: National Cancer Database identified SCLC patients treated with chemotherapy from 2010 - 2014. Factors associated with TCD were identified with multiple linear regression analyses. TCD was categorized into four groups using cutoff points of 7, 14, and 28 days. Using these categories, median overall survival (MOS) and log-rank test was used for univariate analysis of the survival outcome and the Cox model for multivariate analysis. Results: Among the 64491 SCLC, 42% received chemotherapy alone, 38% chemotherapy followed by radiation and 20% radiation followed by chemotherapy. Median TCD is 14 days with 21% treated within 7d, 21% 8-14d, 30% 15-28d and 28% > 28d from diagnosis. Age, race, insurance, comorbidities and stage were associated with TCD (Table). Significant difference in survival was found by TCD categories (P < .001). MOS for TCD within 7d was 8.2m, 8-14d was 9.2m, 15-28d was 10.3m, and > 28d was 10.8m. In the multivariate analysis, increased TCD was associated with better survival across all stages. Among stage IV patients, compared to those treated within 1 week, the HR is 0.92 (P < .001) for 1-2 weeks, HR 0.82 (P < .001) for 2-4 weeks, and HR 0.77 (P < .001) for > 4 weeks. Results are similar for Stage III and for Stage I/II. Conclusions: These results show a trend towards poor survival with early treatment. While we do not suggest delaying treatment for SCLC patients, our results provide new evidence to inform a discussion about appropriate treatment timing and individualizing treatment. Optimization of patients' clinical baseline before hasty cytotoxic treatment may lead to better outcomes. [Table: see text]