In the subgroup analysis for OS according to treatment protocol, elevated NSE did not have significant prognostic value of OS for SCLC patients treated by only chemotherapy in 2 studies [25, 29] with combined HR of 1.22 (95% CI 0.96–1.55, p = 0.10; I2 = 0%, p = 0.32). This evidence concerns the gene ENO2 and small cell lung carcinoma.