The Detection of Radiation Effects in the Urine of Rhesus Macaques Using Raman Spectroscopy

Exposure to ionizing radiation has been associated with the development of neoplasms in humans and other animals. Detection of both neoplastic growth and effects of radiation with standard laboratory testing (hematology and serum chemistry analyses) is problematic. There are no specific biomarkers present in biological fluids (blood, urine) for early detection of neoplastic growth or long-term effects of radiation exposure, but these would be extremely useful for monitoring both treatment efficacy and detecting undesirable side effects in patients undergoing radiotherapy. We conducted a retrospective study of 76 urine samples from rhesus macaques using a novel Raman spectroscopy-based analytical technology (Raman Molecular Urinalysis) to establish a urine fingerprint for past radiation treatment. Forty-nine animals were irradiated (of which 12 developed sarcomas following experimental exposure to total body ionizing radiation) and 27 animals were not irradiated (2 of which developed non-radiation-associated sarcomas). We applied an unsupervised principal component analysis and supervised discriminant analysis of principal components and averaged the spectra. The results showed the groups had a highly similar average spectra, but more variability and outliers existed in the irradiated group of animals. The unique characteristics of these outliers were unclear, and further investigation is needed. Animals with sarcomas had a distinct spectral profile with high specificity and high negative predictive value. A definitive radiation molecular spectral fingerprint was not identified in the urine of irradiated macaques in comparison to unirradiated control animals, but this study provides initial evidence and insights for future research.