**7. Conclusions**

Exosomes play a critical role in cancer progression, including cell–cell communication, tumor-stromal interactions, activation of signaling pathways, and immunomodulation. Emerging data indicate that radiation-derived exosomes increase tumor burden, decrease survival, cause radiation-induced bystander effects and promote radio-resistance. Exosomes show abilities as diagnostic and predictive biomarkers in various malignancies. Exosomes play a role in radio- and chemo-resistance through multiple pathways. The mechanism of the intercellular communication by exosomes, the transport of exosomal cargo, the secretion mechanism, cell dependence, immune response and radiation response have been intensively explored. Specifically, research *Exosomes in Cancer Diagnosis and Radiation Therapy DOI: http://dx.doi.org/10.5772/intechopen.101684*

on exosomes about radiation therapy has been expanding. Radiation-exposed cells release altered exosomes, and those exosomes play a role as cargo to bring multiple messages to their recipient cells leading to various radiation responses. Further understanding of the mechanisms of exosome-mediated radio-resistance might ultimately lead to the development of novel treatment strategies.
