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Dose Fractionation in Radiotherapy
Published in W. P. M. Mayles, A. E. Nahum, J.-C. Rosenwald, Handbook of Radiotherapy Physics, 2021
Gordon Steel, Catharine West, Alan Nahum
During the last 30 years, important new insights have been gained into the principles of dose fractionation in radiotherapy. The linear-quadratic (LQ) approach (see Section 6.11) provided a new understanding of why fractionation works and how it may be optimised; this approach is the standard method of calculation in radiotherapy departments and will be described in detail in this chapter. The practical basis of fractionation was established many years ago, well before the introduction of the LQ approach, through the skill, observation and wisdom of radiation oncologists in France, Austria and other countries. A description of these historical aspects can be found in Thames and Hendry (1987), Joiner and Bentzen (2019), Fowler (2006), Nahum (2015) and Moulder and Seymour (2018).
External Beam Radiotherapy and Brachytherapy
Published in Karl H. Pang, Nadir I. Osman, James W.F. Catto, Christopher R. Chapple, Basic Urological Sciences, 2021
Sophia C. Kamran, Jason A. Efstathiou
Dose fractionation: total radiation dose is divided into a higher dose per treatment for fewer total treatments (hypofractionated radiotherapy, HFX).Reduces toxicity to healthy cells.Utilises the differences in the DNA repair capacity of normal and tumour cells.Allows efficacious tumour killing through the ‘5 Rs’.
Radiation Injury
Published in Peter Sagar, Andrew G. Hill, Charles H. Knowles, Stefan Post, Willem A. Bemelman, Patricia L. Roberts, Susan Galandiuk, John R.T. Monson, Michael R.B. Keighley, Norman S. Williams, Keighley & Williams’ Surgery of the Anus, Rectum and Colon, 2019
There are two different types of toxicity: acute and late on normal tissues. This chapter will discuss the factors involved with timing of the treatment, role of chemotherapy, treatment volumes, dose fractionation, new radiation technologies and possible alternatives to improve the therapeutic index.
An introduction to the special issue of IJRB in honor of the extraordinary legacy of Professor John B. “Jack” Little in the radiation sciences
Published in International Journal of Radiation Biology, 2023
Amy Kronenberg, Edouard I. Azzam
The effect of microenvironmental factors on in vivo radiation responses was actively pursued in the Little laboratory. In the 1990s, Benoît Paquette, then a postdoctoral fellow in the laboratory, showed that the in vivo environment enhances genomic instability in cells transformed by X rays. In their article, Ayman Oweida and Benoît Paquette further review in vivo environmental effects on radiation responses. They present specifically an overview of two opposing effects of radiation therapy, stimulation of cancer cell invasion and activation of anti-cancer immunity. They discuss the molecular and cellular mechanisms involved, the modulating effect of radiation dose and dose fractionation, the intrinsic radiation sensitivity of cancer cells, and the presence in the tumor of cancer associated cells among other factors. They review the preclinical and clinical evidence supporting these seemingly opposing responses, as well as the cytokines, exosomes, and immune cells that may play a role in shifting the balance between anti-tumor and pro-tumor effects of radiation exposure. They show how understanding of these mechanistic aspects is leading to strategies that block various stages of cancer progression and lead to tumor regression.
Biomarkers for translational oncology – Peggy Olive’s contribution
Published in International Journal of Radiation Biology, 2022
Many factors are known to influence a tumor's response to radiation therapy (RT), including total dose, fractionation, tumor doubling time, hypoxia and intrinsic radiosensitivity. (Meehan 2020). Hence, if tumor radiosensitivity could be predicted in advance, it may be possible to improve radiation therapy procedures significantly by selecting patients whose tumors are radiosensitive and to identify earlier those who would benefit from surgery. Biomarkers in oncology are considered as endpoints that can be used to define and differentiate between benign and malignant tissues and their response to radiation therapy. Of these, predictive biomarkers are highly important for personalization in RT. Moreover, biomarkers have unexplored potential for predicting the extent of subclinical spread of tumor cells to help define the clinical target volume. Thus, clinically-validated biomarkers can help clinicians assess a tumor's response to RT during treatment to successfully implement personalized radiation treatment (PRT).
Topical application of Jatyadi Ghrita and Jatyadi Taila accelerates wound healing in Sprague-Dawley rats: a study in gamma-radiation-induced skin wound model
Published in International Journal of Radiation Biology, 2021
Vanita Gupta, Anuradha Tyagi, Aseem Bhatnagar, Sukhvir Singh, Sudesh N. Gaidhani, Narayan Srikanth
Radiotherapy accounts for almost 95% occurrence of radiation wounds as a side effect of cancer treatment with 10% being the severe one (Ryan 2012; Singh et al. 2016). Even though radiation technology has improved a lot but radiation wounds are still a major cause of concern during radiotherapy (Singh et al. 2016). The radiation dose delivered, dose fractionation, size of the skin surface area exposed, body mass index, and sequential chemotherapy are the major factors that determines the course and severity of radiation wounds. Also, area of body containing skin folds such as breast and groin are at a higher risk of developing skin reactions (Ryan 2012). Researchers worldwide are still working on development of animal models for radiation dermatitis for better understanding of the pathophysiology of radiation wounds and for developing remedies that can mimic the clinical conditions (Sheng et al. 2019; Kulshrestha et al. 2020).