Prognostic Value of Serum Lactate Dehydrogenase (LDH) Levels in Small Cell Lung Cancer Patients Receiving Thoracic Radiotherapy and Prophylactic Cranial Irradiation

Role of LDH in SCLC

Abstract

Objective: Small cell lung cancer (SCLC) accounts for 15% of all lung cancers and is more aggressive than other types of lung cancer. In these cases, the most important prognostic factor is the presence of brain metastases. According to the National Comprehensive Cancer Network Guidelines, prophylactic cranial irradiation (PCI) is a treatment option to prevent brain metastasis. However, brain metastases develop within four years in 45% of patients despite PCI. Therefore, it is important to identify predictive factors for brain metastases. Serum lactate dehydrogenase (LDH) levels have long been recognized as a prognostic factor in many cancer contexts. In this study, we aim to evaluate the relationship between serum LDH levels and intracranial progression-free survival (ICPFS) as well as overall survival (OS) in SCLC patients receiving PCI and thoracic radiotherapy (TRT).
Methods: This study evaluated 50 patients who underwent PCI and TRT for SCLC between July 2012 and April 2024. Pre-treatment serum LDH levels and maximum serum LDH (mLDH) levels were recorded during the study. An increased serum LDH level was defined as a value exceeding 346 IU/mL. The relationship between serum LDH levels, OS, and ICPFS was evaluated using Kaplan-Meier analysis.
Results: The median mLDH level was determined to be 346 IU/L. Of the total number of patients (n=50), 25 exhibited elevated mLDH levels. No differences were observed between patients with normal and elevated mLDH levels regarding their characteristics. The median ICPFS for the elevated and normal mLDH groups was 15 and 29 months, respectively (p=0.01). The median OS was 25 months in the elevated mLDH group and was not reached in the normal mLDH group (p=0.034). In the multivariate analysis, only mLDH levels were independently associated with OS (hazard ratio: 3.92; 95% confidence interval: 1.15-13.3; p=0.02).
Conclusion: Serum mLDH levels during TRT and PCI predict intracranial progression and survival in SCLC patients, helping identify at-risk patients who may benefit from aggressive treatment.