What is Cancer?• A disease involving abnormal cell growth that can spread to
other parts of the body
Causes/Symptoms• Causes• 90% Environmental (carcinogens from tobacco/food, radiation,
infection, lifestyle)• 10% Genetic/hereditary
• Symptoms• Dependent on cancer type
Closer look: Radiotherapy• Can damage normal cells• Different cancer types have different radiosensitivity• High (leukemia, lymphoma, ovarian/testicular), ~30 Gy• Moderate (breast, prostate, lung, colon), ~70 Gy• Low (skin, kidney), too high to be safe
• Curability is usually reverse of radiosensitivity• Therefore usually requires chemotherapy
• Intensity vs exposure constraint
Advances in Radiotherapy• Advanced image guiding systems – higher precision• SABR (stereotactic ablative body radiation)• Synchrotron MRT (microbeam radiotherapy)• Pre-clinical testing due to unknown reason for low local tissue
sensitivity
Synchrotron MRT• High flux X-rays segmented into a lattice of micro-planar
beams separated by plains of low dose radiation, allowing very high doses (over 100 Gy) of radiation
Closer Look: Immunotherapy• Mechanism: body’s immune system will fight cancer cells• Three “E”’s of immunoediting• Elimination• Equilibrium• Escape
• Limited to cancer cells which release high immunoactivators• Cancer cells which release little/no immunoactivators are not
affected
Elimination• Cancer cells release immunoactivators which act as receptors
for white blood cells to target
Combining Radiotherapy and Immunotherapy• Positive Effects (2-15 Gy)• Irradiated cancer cells are a good source of diverse
immunoactivators• Radiation activates MHC class I receptors in cancer cells, releasing
more immunoactivators• New immunoactivators are memorized and used for secondary
cancers• Negative Effects (Over 15 Gy)• Cancer cells enters “wound healing” state when dosage is too
high, releasing immunosupressant chemicals• Immunosupressant chemicals prevent/inhibit release of
immunoactivators such has MHC class I receptors
Conclusion• Radiotherapy has become more precise due to technological
advancement• Immunotherapy is limited to cancer cells which release
enough immunoactivators• Radiotherapy can allow utilization of irradiated cancer cells in
immunotherapy to increase effectiveness, with low radiation doses more effective in this case
References• http://
www.sciencedirect.com/science/article/pii/S0304383515000300
• http://www.annualreviews.org/doi/abs/10.1146/annurev.immunol.22.012703.104803
• http://www.cancernetwork.com/cancer-management• http://www.who.int/mediacentre/factsheets/fs297/en/
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