The following section is on a treatment of cancer, it is not a guide on how to perform it, nor is it a guide as to the side effects or how to prepare for treatment. The following section is designed to give readers an in-depth understanding of the treatment, how it functions, and why it functions. Please note that researchers are constantly working to find new treatments or improve current ones, this means the subject(s) discussed below are likely to change as medicine improves.
Radiotherapy is a newer treatment that can be slightly unintuitive, as previously covered radiation is a possible cause for cancer, so to clear up confusion this segment will cover a few current uses of radiotherapy in cancer treatment.
Generally as covered in the section on causes of cancer, radiation with enough energy can be powerful enough to alter the chemical structure of molecules such as DNA. Additionally not all mutations cause cancer, cancer requires specific mutations in parts of the DNA that regulate cell replication, but still need most of the other DNA to be functioning so the cells can survive. By introducing controlled levels of radiation to tumors the radiation can destroy enough DNA so as to leave the cell unable to function leading to cell death. Cell death induced by radiotherapy can also sometimes attract immune cells as cancer cells may have unusual proteins within them ,due to the damaged DNA, that is then released upon cell death. (1)
Deciding how much radiation to give will be left to medical textbooks as it is highly nuanced and is decided on a case by case basis. However, a part that can be covered is how the radiation is actually delivered, below are the two current ways of delivering radiotherapy.
External beam radiotherapy (EBRT) is a common type of radiotherapy, usually using a linear accelerator or LINAC. LINAC machines spin around the patient delivering targeted beams of radiation. Medical staff use imaging parts of the machine to monitor the tumor’s position so as to limit damage to nearby healthy cells.
However mapping the tumor and shooting radiation at it from an outside source would still cause the most cellular damage to the tissue between the source of the radiation and the tumor, this is shown in Fig 1, the density of the color shows an approximation of the intensity of a beam of radiation. This is why LINACs spin around the patient delivering less radiation on all points, however by targeting all of the beams at the tumor the tumor receives the most radiation as shown in Fig 2.
Brachytherapy is a form of internal radiation therapy. This form of therapy implants small radioactive materials inside the body, usually in the form of pellets/beads or strings. Generally this is beneficial as higher doses of radiotherapy can be used than in external beam radiotherapy, as placing the source of radiation within the person can limit the damage to surrounding healthy tissue.
Brachytherapy can be broadly classified as either high or low dose radiotherapy. High dose brachytherapy is often only inserted into the patient for a few minutes before being removed. Low dose brachytherapy is left in the body permanently or could decompose in the body. Usually these are small pellets about the size of a grain of rice.
(2)
| 1. | Alhmoud J, Al Moustafa AE, Malki M. Checking your browser – reCAPTCHA. Nih.gov. Published 2026. Accessed July 11, 2026. https://pmc.ncbi.nlm.nih.gov/articles/pmc7226105/#sec8-cancers-12-01050 |
| 2. | Mayo Clinic. Brachytherapy – Mayo Clinic. Mayoclinic.org. Published 2018. Accessed July 12, 2026. https://www.mayoclinic.org/tests-procedures/brachytherapy/about/pac-20385159 |