Temporal trends in small cell lung cancer: Analysis of the U.S. Surveillance, Epidemiology and End Results (SEER) database.

Abstract

e20641 Background: Prior studies reported that the incidence of small cell lung cancer (SCLC) had decreased, while overall survival (OS) had improved, from 1973-2002. In 2019, immunotherapy was integrated into the standard therapy for patients with extensive-stage (ES) SCLC based on studies demonstrating an improvement in OS. This study aims to provide an update on SCLC incidence and survival at the dawn of this new therapeutic age. Methods: We analyzed data on all patients with primary lung cancer in the SEER17 database from 2000-2019. Patients with ICD-O codes 8002 and 8041-8044 were classified as SCLC. Incidence rates were calculated based on the standard U.S. population. OS was calculated based on censored time to death or last follow-up, whichever occurred earlier. Temporal trends in incidence and OS were evaluated using the Mantel-Haenszel chi-square statistic. Results: Of 847,747 patients with primary lung cancer, 111,263 (13.1%) had SCLC. The incidence rate of SCLC steadily declined from 8.8/100,000 in 2000 to 4.8/100,000 in 2019. Over this time, the incidence rate decreased among both males (10.7 to 5.1/100,000) and females (7.5 to 4.6/100,000), and among all examined races (NHW: 10.1 to 6.0/100,000, NHB: 8.3 to 4.7/100,000, NHA/PI: 3.5 to 1.6/100,000, Hispanic: 4.0 to 1.9/100,000). The proportional incidence of SCLC relative to NSCLC also continued to decline, from 14.5% in 2000 to 11.8% in 2019. The male:female ratio of SCLC patients decreased from 1.14:1 in 2000 to 0.93:1 in 2019. The percentage of patients with limited-stage (LS) SCLC decreased from 31.1% in 2000 to 26.4% in 2019. The majority of patients with LS-SCLC were female throughout the study period (53.9%), while most of those with ES-SCLC were male (51.8%). Among patients with LS-SCLC, 2-year OS increased from 26.7% in 2000 to 36.7% in 2017, while 5-year OS increased from 11.3% in 2000 to 15.6% in 2014. Among patients with ES-SCLC, 2-year OS increased from 6.4% in 2000 to 8.4% in 2017, while 5-year OS increased from 2.2% in 2000 to 2.9% in 2014. Both 2-year and 5-year OS increased in LS-SCLC over the study period in both males and females (M: 2-year: 23.4% to 36.2%, 5-year: 9.9% to 15.2%; F: 2-year: 29.9% to 37%, 5-year: 12.8% to 16.0%). In ES-SCLC, 2-year OS increased in both males and females (M: 5.8% to 7.3%, F: 7.0% to 9.5%), while 5-year OS increased in females (2.2% in 2000 to 3.9% in 2014), but remained stable in males (2.3% in 2000 to 2.0% in 2014). Conclusions: Both the incidence and proportional incidence of SCLC have continued to decline in the U.S. over the past 20 years. The male:female ratio also declined, with women now accounting for the majority of patients with SCLC. The percentage of patients with LS-SCLC decreased, likely due to improvements in staging procedures. Overall survival has continued to improve, with greater gains seen in LS-SCLC than in ES-SCLC prior to the integration of immunotherapy.