Particle therapy and cancer treatment
This is due to their higher mass-to-charge ratio when compared to protons, which means that they experience less deviation and deflection. This allows for even more precise targeting of the cancer with fewer side effects. CIRT has also been estimated to be more effective at targeting tumours than photon and proton therapy by a factor of 2.5-5. This is in turn due to their increased charge which attracts electrons more strongly from atoms, as well as their larger mass causing more powerful collisions with other atomic nuclei to produce additional particles. 9 Moreover, it may be a viable treatment for some very radioresistant cancers. These cancers are often hypoxic, meaning that the cancer cells can survive and multiply in very low oxygen conditions, so ROS have much less effect on the cells’ DNA. Carbon ion therapy has been observed to cause more direct DNA damage than photons, limiting the need for ROS activity. A study from Japan 10 found an increased frequency of double-strand breaks in tumour specimens irradiated with carbon ions compared to photons. The double-strand breaks induced by the carbon ions were also much more complex and almost impossible for the cancer cells to repair, leading to more frequent cell death. A possible disadvantage of CIRT is the small exit dose (Fig. 4) which results from nuclear fragmentation, which produces lighter, longer-range particles such as neutrons. Results in animal models have been promising, showing increased relative biological effectiveness against all cancers when compared to photons. In humans, 56.3% of patients survived 5 years post-diagnosis with CIRT, compared to around 15% with standard of care. 11 Unfortunately, there is a lack of controlled studies comparing CIRT to photon or proton therapy, so more research is needed to directly compare the effectiveness of these therapies. In conclusion, I believe that particle therapy does hold much promise for cancer treatment. Photon treatment is simply too damaging, imprecise and toxic to continue to be used as the gold standard for radiotherapy. Particle therapy could achieve the same high levels of effectiveness against cancer without compromising the patient’s quality of life. In my view, carbon ion t herapy has the most potential out of these treatments. It has the same dosing advantages as proton therapy, allowing for minimal damage to healthy tissues. However, its winning quality is its increased effectiveness compared to both photon and proton therapies, as well as its relative ease compared to antiproton therapy. For these reasons, I firmly believe that carbon ion therapy will become the prime cancer treatment modality in the future.
References
1. https://www.cancerresearchuk.org/health-professional/cancer-statistics/worldwide-cancer [consulted 21/08/2021]. 2. Kufe DW, Pollock RE, Weichselbaum RR, et al. Holland-Frei Cancer Medicine (2003). Available at https://www.ncbi.nlm.nih.gov/books/NBK13943/ . 3. https://www.nhs.uk/conditions/radiotherapy/side-effects/ [consulted 21/08/2021]. 4. Baskar R, Dai J, Wenlong N, et al. (2014) ‘Biological response of cancer cells to radiation treatment’. Frontiers in Molecular Bioscience, 1:24 available at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4429645/; and see also Newhauser W, Zhang r. (2015) ‘The physics of proton therapy’. Physics in Medicine & Biology, 60(8) available at https://iopscience.iop.org/article/10.1088/0031-9155/60/8/R155. 5. Mitteer R, Wang Y, Shah J et al. (2015) ‘Proton beam radiation induces DNA damage and cell apoptosis in glioma stem cells through reactive oxygen species’. Scientific Reports, 5 available at https://www.nature.com/articles/srep13961#Sec11.
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