Exhaled Breath Analysis for Head and Neck Cancer Using Fourier-Transform Infrared Spectroscopy: A Feasibility Study for Non-Invasive Screening

<b>Background/Objectives:</b> Early detection and intervention are critical for improving outcomes in head and neck cancer. Although endoscopy is commonly used for screening, it requires specialist expertise and may cause patient discomfort. Therefore, there is a need for a simpler and less invasive screening method. This study aimed to evaluate the clinical feasibility of Fourier-transform infrared (FTIR) spectroscopy-based exhaled breath analysis as a non-invasive screening tool for head and neck cancer. <b>Methods:</b> This single-center study was conducted at the Department of Otolaryngology-Head and Neck Surgery, Showa Medical University. Outpatients with head and neck cancer (<i>n</i> = 10) and healthy controls (<i>n</i> = 14) were enrolled. Exhaled breath samples and ambient air surrounding the patient and lesion were analyzed using FTIR spectroscopy. Infrared absorption spectra were obtained, divided into 7667 discrete wavenumber points across the measured range, and compared between the patient and control groups. <b>Results:</b> FTIR spectroscopy revealed significant differences between patients and controls, with 2691 wavenumber points showing statistically significant differences (<i>p</i> < 0.05). Among these, the wavenumber at 3917.3 cm^-1 showed a particularly strong difference (<i>p</i> = 0.00015). Receiver operating characteristic analysis demonstrated good discriminative performance, with an area under the curve of 0.929. The maximum Youden index was 0.829, with an optimal threshold of 0.234. <b>Conclusions:</b> FTIR-based exhaled breath analysis is a non-invasive and feasible approach for screening head and neck cancer. These findings suggest that this technique has potential clinical applicability as a screening tool and may also be extendable to the detection of other diseases.