Telomere length and oxidative stress in small cell lung cancer patients: changes through chemotherapy cycles compared to healthy controls.

Introduction: Small cell lung cancer (SCLC) is an aggressive malignant disease with poor survival outcomes. The aim of this study was to investigate leukocyte telomere length (LTL) and redox status parameters during chemotherapy and evaluate their prognostic potential based on the hypothesis that shorter LTL and oxidative stress burden correlate with poorer survival. Materials and methods: This longitudinal study included 60 SCLC patients and 73 healthy controls. Leukocyte telomere length was measured by quantitative PCR (qPCR) method, while redox status parameters (MDA - malondialdehyde, IMA - ischemia-modified albumin, PON1 - paraoxonase 1, redox index) were determined by spectrophotometric methods before, after two and after four cycles of chemotherapy. Results: All measured parameters showed significant differences between patients and controls, except the oxy-score (P < 0.001). Significant differences in IMA, PON1 and redox index were observed between SCLC patient groups at different time points (P < 0.001). Significant differences in IMA and PON1 were observed between SCLC survival groups, with higher values found in survivors after two chemotherapy cycles (P < 0.001). Redox index was the highest in the pre-chemo group (P = 0.019). Among patients who died, PON1 activity differed significantly between those who died within 2 months and after 4 months (P = 0.028). Kaplan-Meier analysis showed that LTL and PON1 were significant predictors of survival, with values below the 25th percentile associated with a higher risk of death. Conclusions: Leukocyte telomere length and PON1 are potential prognostic biomarkers for SCLC survival, suggesting their potential use in non-invasive biomarker panels for improved patient stratification.