Summary: | Conventional external beam radiotherapy uses photons to irradiate and kill tumor cells. The photon dose is delivered to the tumor in a continuous beam that can damage surrounding tissues. New photon technologies such as intensity modulated radiotherapy (IMRT) and stereotactic radiotherapy aim to reduce collateral tissue damage through more comprehensive planning and advanced technology that enables more direct targeting of the tumor, but none of these techniques can completely prevent downstream damage caused by the exit dose of a photon beam. An alternative to photon therapy -- proton beam therapy (PBT) -- uses protons, which deposit less energy before and after the tumor. This is due to a phenomenon called the Bragg peak, which allows the most energy to be released near the end of the proton path, effectively delivering the greatest dose to the exact tumor location. There is much interest in increasing the availability of PBT in Canada, but increased costs, implementation concerns, and unsubstantiated comparative clinical benefit and harms compared to other cancer radiotherapy treatments should be considered. This review will evaluate evidence on the comparative clinical and cost-effectiveness of PBT and photon radiotherapy in adult and pediatric patients requiring radiotherapy for the treatment of cancer
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