Spontaneous photon emission: A promising non-invasive diagnostic tool for breast cancer.

Ultra-weak photon emission (UPE) has attracted significant scientific attention for its potential to monitor the physiological and pathological characteristics of living systems. In this study, we investigated the strength of spontaneous photon emission (SPE) from the right (R) and left (L) side of body surface of human breast cancer-bearing nude mice models, considering the entire breast cancer growth process, and healthy controls using a photon detector. And then we calculated the ratio of the average SPE strength (ratio (R/L)) between the right and left side of each mouse. Cluster analysis was used to evaluate the accuracy rates of strength-R, strength-L, ratio (R/L) and their combination to identify tumor mice from the controls. Our results revealed that the discriminating powers of different parameters were different in different growth stages of tumor: in tumor incubation period, the accuracy rates of strength-R, strength-L, ratio (R/L) and their combination to identify tumor mice from control mice were 63.6%, 40.9%, 81.8% and 86.4%, respectively; For nude mice with tumor diameter <0.5cm, the accuracies were 72.7%, 45.5%, 86.4% and 90.9%; and for nude mice with tumor diameters larger than 1.5cm, the accuracies were 86.4%, 77.3%, 95.5% and 100%, respectively. These results indicated that the SPE from the body surface of the lesion site could significantly distinguish tumor mice from the controls when tumors were obvious or when there were no obvious morphological changes, although the accuracy was relatively low. The results suggest that SPE, as a sensitive and promising optical method, may contribute to the preliminary screening of breast cancer, especially for early diagnosis, and it may play a critical role in curtailing the effects of breast cancer and improving the survival of patients in the future.