Proton Magnetic Resonance Spectroscopy of Sputum for the Non-Invasive Diagnosis of Lung Cancer: Preliminary Findings

Abstract

Aims and Background: Sputum has been examined for the identification of potential biomarkers for the non-invasive diagnosis of lung cancer. However, no definitive biomarkers with reliable accuracy have been identified yet. The main objective of this work was to evaluate the utility of magnetic resonance spectroscopy (MRS) in the analysis of sputum for the non-invasive diagnosis of lung cancer. Methods: Induced sputum samples from lung cancer patients (n = 9) and control subjects (n = 6) were collected for proton (1H) MRS analysis. Samples from two cancer patients and one control subject were discarded as these samples were confirmed to contain only saliva by cytologic examination. Only the true sputum specimens containing alveolar macrophages were analyzed by 1H MRS. To facilitate MRS analysis, sputum samples were dispersed in 2M sodium chloride solution buffered with phosphate-buffered-saline (PBS). MR spectra were obtained using a one-pulse sequence with presaturation of the water resonance. Results: Glucose was found to be absent in sputum samples obtained from lung cancer patients. Spectra of sputum samples collected from control subjects showed presence of glucose signal except for one whose sputum cytology indicated the presence of atypia. The absence of glucose in sputum from cancer patients could be attributed to an increased rate of glycolysis in the lung cancer cells. The present observation, albeit on a small sample size, showed a better sensitivity (100%) and overall accuracy (92%) compared to sputum cytology (sensitivity = 50%; overall accuracy = 70%). Conclusions: Absence of glucose in sputum could be an indicator of lung cancer and the present methodology can be a valuable addition to the non-invasive diagnostics of lung cancer.