Background: Early detection is crucial to improve lung cancer survival rates. Delays in diagnosis might negatively impact the prognosis of the disease. This study aims to analyze the diagnostic delay in lung cancer patients and describe if there is an association between delay and survival.

Methods: The data source used was the Thoracic Tumour Registry of the Spanish Lung Cancer Group. This analysis was restricted to lung cancer cases with information on the first date of consultation by symptoms and date of diagnosis. The delay was calculated as the number of days between the two dates. A descriptive analysis was performed, and ordinal logistic regressions were fitted with delay as the dependent variable. Kaplan-Meier survival analysis and Cox regression were performed.

Results: 22,755 cases were included. Never smokers were 1.16 (95%CI:1.06-1.27) times more likely to register longer delay than smokers. Stage 0-I-II cases had a 3.09 (95%CI:2.88-3.32) higher risk of longer delay compared to III-IV stages. Overall, 5-year survival rate after diagnosis was 23.64% (95%CI: 22.88-24.41). In those categorized as having the shortest delay 5-year survival was 17.67% (CI95%:16.31-19.07) and in the extreme delay it was 32.98% (CI95%: 31.28-34.69) (p<0.005). Adjusted mortality risk was higher in those with the shortest delay (HR 1.36, CI95%:1.30-1.43) in comparison with the extreme delay.

Conclusions: Diagnostic delay is short among Spanish lung cancer patients, indicating a relatively quick diagnostic process. Extreme delays appear to be associated with higher survival rates, possibly attributed to slow-growing tumors, earlier stage at diagnosis or basically the natural history of this disease.