Electrophysiological markers of subclinical central nervous system involvement in patients with non-small-cell lung cancer without brain metastases

AIM OF THE STUDY: To evaluate electrophysiological parameters of central nervous system (CNS) function in patients with non-small-cell lung cancer (NSCLC) without detectable CNS metastases. CLINICAL RATIONALE FOR THE STUDY: Early recognition of nervous system involvement in lung cancer (LC) is important for the management of the disease. Evoked potentials are an objective and noninvasive method for assessing CNS bioelectrical activity, regarded as a useful tool in revealing subclinical CNS dysfunction in systemic diseases, including neoplasms. MATERIAL AND METHODS: The study included 11 patients (mean age 67.3 years, 55% females), diagnosed with NSCLC, without CNS metastases, and a group of 24 healthy controls (HC) matched for age. All participants underwent brainstem auditory evoked potentials (BAEP), visual evoked potentials (VEP) and electroencephalography (EEG). Parameters of VEP and BAEP were compared between LC patients and HC. In the NSCLC group, they were also referred to the disease outcome evaluation after 12 months of follow-up. RESULTS: In VEPs, patients with NSCLC had significantly longer median P100 and N145 latencies compared to the HC (112 vs. 104 ms, p < 0.001 and 158 vs. 145 ms, p = 0.002, respectively). In BAEPs, longer median latency of wave V and I-V interpeak latency were found in NSCLC patients (5.88 vs. 5.80 ms, p = 0.047 and 4.19 vs. 4.05 ms, p = 0.007, respectively); they also had significantly lower median amplitudes of I and V waves (0.13 vs. 0.25 μV, p < 0.001 and 0.29 vs. 0.39 μV, p = 0.001, respectively). In total, 10 out of 11 patients showed abnormalities in either VEP or BAEP: in 4 patients, delayed latencies or decreased amplitudes were detected for both modalities, in 4, only in BAEP and in 2, only in VEP. EEG abnormalities were detected in two patients in the NSCLC group. After 12 months of follow-up, in none of the patients brain metastases were revealed. CONCLUSIONS AND CLINICAL IMPLICATIONS: This exploratory study demonstrated abnormalities of EP parameters in NSCLC patients, without otherwise detectable CNS involvement. These findings may suggest subclinical brain dysfunction in the course of NSCLC, although the underlying mechanism remains uncertain. The usefulness of electrophysiological methods in monitoring or predicting subtle neurological complications of NSCLC warrants further investigation.