Application value of serum LDH in advanced non-small cell lung cancer patients treated with EGFR-TKI

Objective To investigate the value of serum lactate dehydrogenase (LDH) in advanced non-small cell lung cancer (NSCLC) treated with epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitor (TKI). Methods Pretreatment LDH level, pathological characteristic, tumor staging and treatment situation of 190 advanced NSCLC patients with EGFR sensitive mutation confirmed by pathology were retrospectively collected in Zhuhai People′s Hospital of Guangdong Provice from July 2011 to July 2015. All the patients were divided into LDH normal group (LDH≤252 U/L, n=78) and elevated group (LDH>252 U/L, n=112) according to pretreatment LDH level. Imaging evaluations of the patients were performed regularly, and the progression-free survival (PFS) and overall survival (OS) were recorded. The survival curves were plotted by Kaplan-Meier method and survival difference between patients with different LDH level was compared by log-rank test. Cox regression analysis was used to analyze prognostic factors for mortality. Results The objective response rate of the LDH normal group was 76.9% (60/78), and the elevated group was 71.4% (80/112), with no statistically significant difference (χ2=0.716, P=0.398). The disease control rate of the LDH normal group was 89.7% (70/78), and the elevated group was 85.7% (96/112), with no statistically significant difference (χ2=0.676, P=0.411). The median PFS of the LDH normal group was 11.5 months, and the elevated group was 9.7 months (χ2=5.92, P=0.015). The median OS was 31.0 months in the LDH normal group, and 26.1 months in the elevated LDH group (χ2=4.79, P=0.029). Both PFS and OS of patients with elevated LDH were shorter than those of patients with normal LDH. Cox multivariate regression analysis showed that tumor staging (HR=1.652, 95%CI: 1.386-2.259, P=0.018), PS score (HR=2.248, 95%CI: 1.507-3.846, P<0.001), carcino-embryonic antigen (CEA) level (HR=1.250, 95%CI: 1.066-1.703, P=0.037) and LDH level (HR=1.771, 95%CI: 1.324-1.947, P=0.015) were independent prognostic factors in patients with advanced NSCLC. Conclusion Pretreatment serum LDH can not affect the objective response rate and disease control rate of EGFR-TKI in the treatment of advanced NSCLC, but can affect the PFS and OS of patients. Pretreatment serum LDH is an independent prognostic factor. Key words: Lactate dehydrogenase; Carcinoma, non-small cell lung; Epidermal growth factor receptor-tyrosine kinase inhibitors; Prognosis