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High‐dose‐rate‐brachytherapy (HDR‐BT) is an increasingly attractive alternative to external beam radiation‐therapy for patients with intermediate risk prostate cancer. Despite this, no bio‐marker based method currently exists to monitor treatment response, and the changes which take place at the biochemical level in hypo‐fractionated HDR‐BT remain poorly understood. The aim of this pilot study is to assess the capability of Raman spectroscopy (RS) combined with principal component analysis (PCA) and random‐forest classification (RF) to identify radiation response profiles after a single dose of 13.5 Gy in a cohort of nine patients. We here demonstrate, as a proof‐of‐concept, how RS‐PCA‐RF could be utilised as an effective tool in radiation response monitoring, specifically assessing the importance of low variance PCs in complex sample sets. As RS provides information on the biochemical composition of tissue samples, this technique could provide insight into the changes which take place on the biochemical level, as result of HDR‐BT treatment. [ABSTRACT FROM AUTHOR]

Tumour heterogeneity plays a large role in the response of tumour tissues to radiation therapy. Inherent biological, physical, and even dose deposition heterogeneity all play a role in the resultant observed response. We here implement the use of Haralick textural analysis to quantify the observed glycogen production response, as observed via Raman spectroscopic mapping, of tumours irradiated within a murine model. While an array of over 20 Haralick features have been proposed, we here concentrate on five of the most prominent features: homogeneity, local homogeneity, contrast, entropy, and correlation. We show that these Haralick features can be used to quantify the inherent heterogeneity of the Raman spectroscopic maps of tumour response to radiation. Furthermore, our results indicate that Haralick-calculated textural features show a statistically significant dose dependent variation in response heterogeneity, specifically, in glycogen production in tumours irradiated with clinically relevant doses of ionizing radiation. These results indicate that Haralick textural analysis provides a quantitative methodology for understanding the response of murine tumours to radiation therapy. Future work in this area can, for example, utilize the Haralick textural features for understanding the heterogeneity of radiation response as measured by biopsied patient tumour samples, which remains the standard of patient tumour investigation. [ABSTRACT FROM AUTHOR]

The tumor immune microenvironment is a determinant of response to cancer immunotherapy and, in many cases, is prognostic for patient survival independently of the type of treatment. Radiation therapy is used in most cancer patients for its direct cytotoxic effects on malignant cells but there is increasing evidence that it also reprograms the tumor immune microenvironment. In this review we discuss the main mechanisms whereby the local inflammatory reaction induced by radiation can reset the cross-talk between the tumor and the immune system. The outcome reflects the balance between immunostimulatory signals that lead to increased tumor antigen presentation and effector T cell activation, and immunosuppressive signals that hinder radiation-induced tumor rejection. The emerging role of small extracellular vesicles (exosomes) in this process will be discussed. Overall, preclinical and early clinical findings support the hypothesis that radiation has the potential to generate an immune-permissive tumor microenvironment. An improved understanding of the pathways involved will enable the design of more effective combinations of radiation and immunotherapy, based on a rationale integration of radiation with other interventions. [ABSTRACT FROM AUTHOR]