Non-invasive biomarkers in lung cancer.

Lung cancer is the leading cause of cancer-related deaths worldwide, with its high mortality rate largely due to challenges in early detection. Blood- and tissue-based biomarkers are widely used for diagnosis; however, they often cause patient discomfort, require complex analytical methods, and rely heavily on expert interpretation for disease staging. Non-blood-based biomarkers from sputum, urine, saliva, sweat, and exhaled breath are emerging as effective alternatives for lung cancer diagnostics. These methods are non-invasive, cost-effective, and allow safer, repeated sampling, making them suitable for prognostic use. Urine contains biomarkers such as volatile organic compounds (VOCs) and circulating tumour DNA, providing valuable metabolic insights. Saliva offers proteins, microRNAs, and exosomal biomarkers that reflect systemic disease-related changes. Sputum contains diverse molecular markers that aid early detection. Exhaled breath carries microRNAs and VOCs, representing another promising diagnostic route. Overall, non-invasive biomarker platforms significantly reduce procedural risks and enable earlier lung cancer detection. Their advancement holds substantial potential to improve patient outcomes globally.