Radiation Therapy

Boron neutron capture therapy used to need a nuclear reactor. These hospital-sized accelerators make the neutron beam instead, and in 2020 Japan approved the first one, with its boron drug, for head and neck cancers that have come back or cannot be removed.

Radiotherapy to the head and neck can permanently dry the mouth. A randomised trial in the United States and China found that acupuncture given during radiotherapy reduced dry mouth a year later compared with standard care, an effect that needs confirming.

Re-shaping the treatment plan to the anatomy of the day, using the images taken on the treatment couch, so the dose follows a shrinking tumour or a moving bladder.

Software that draws organs and tumours on scans automatically, saving hours per patient and making daily plan adaptation practical.

A radiotherapy machine with PET detectors built in: the tumour's own radioactive tracer signal tells the beam where to fire, hundreds of times a second, so moving tumours and several metastases can be tracked and treated without external markers.

In boron neutron capture therapy a boron drug accumulates in tumour cells, then a neutron beam makes only those cells explode from inside.

New bowel symptoms after radiotherapy to the prostate, cervix, womb, bladder or rectum are common and are often treated as something to live with. They usually have several separate and treatable causes, and a trial showed that working through them with a written algorithm, delivered by a nurse or a gastroenterologist, improved symptoms more than a self-help booklet.

Brachytherapy places a radioactive source directly inside or next to the tumour.

The standard radiotherapy machine: an electron accelerator in a rotating arm that makes high-energy X-rays or electron beams, shapes them with moving metal leaves, and takes a CT of the patient before each dose. Most people who have radiotherapy are treated on one.

Carbon ions are twelve times heavier than protons, so every clinical facility uses a synchrotron ring tens of metres across and fixed or huge rotating beamlines. Only about a dozen centres exist, in Japan, Germany, Italy, Austria, China, South Korea and Taiwan.

Heavier charged particles that kill even radiation-resistant tumours, available at only a handful of centres worldwide.

The machine that made curative radiotherapy widely available from the 1950s: a sealed cobalt-60 source in a rotating head. Linacs replaced it in rich countries, but cobalt units still treat many patients where power and servicing are unreliable.

A small accelerator on an industrial robot arm that aims hundreds of pencil-thin beams from any direction and follows the tumour as the patient breathes, so brain, spine, prostate, lung and pancreatic tumours can be treated in one to five sessions without a head frame.

Instead of one uniform dose, the plan gives more to the parts of the tumour that imaging says are most resistant, such as hypoxic or highly active regions on PET.

Radiotherapy to the head and neck damages the salivary glands and, through the dry mouth that follows, the teeth. Planning that steers dose away from the parotid glands roughly halves lasting dryness and lets saliva recover over a year or two. Teeth need a dental assessment before treatment starts, because extractions afterwards risk the jawbone failing to heal.

Electron beams stop within a few centimetres of the skin, so they treat surface tumours, scars and the whole skin without reaching the organs underneath. Most linacs make them; special set-ups spread them over the entire body or deliver them during surgery.

Delivering an entire dose in under a second, which in animals spares healthy tissue while still killing the tumour.

Machines built or modified to deliver a whole radiation dose in a fraction of a second, so scientists can test whether ultra-fast dosing spares healthy tissue in people the way it does in animals.

The original radiosurgery machine: about two hundred cobalt-60 sources arranged in a shielded helmet whose beams cross at one point inside the brain, so a metastasis or benign tumour a few millimetres across receives a destructive dose in a single visit while the brain around it is spared.

Oral glutamine, an amino acid that gut and mouth lining cells use for fuel, may reduce the severity of mouth ulcers during head and neck chemoradiation; mucositis guidelines suggest it for that use. Intravenous glutamine in transplant patients is not recommended, and evidence for preventing nerve damage is thin.

A tiny, intensely radioactive source is stepped through applicators placed in or beside the tumour for a few minutes at a time, then withdrawn, so the dose is delivered from inside without leaving anything behind.

Swallowing honey before and after head and neck radiotherapy sessions reduced mouth ulcers in several small trials, mostly from single centres, but the studies are of low quality and mucositis guidelines could not make a recommendation either way.

Breathing pure oxygen in a pressurised chamber, over 30 to 40 sessions, helps heal radiation damage to the jaw, bladder and bowel that appears years after treatment. A Cochrane review found moderate-quality evidence of benefit for these sites, and little for others.

Hyperthermia heats tumours to 40-43 °C to make radiation and chemotherapy work better.

Machines that warm a tumour to about 40 to 43 degrees for an hour using radio waves or microwaves from outside the body, making the radiotherapy or chemotherapy given alongside work better. Few hospitals own one.

Fewer, larger daily doses instead of the classic five to seven weeks of small ones. Large trials in breast and prostate cancer showed the same control with the same or fewer late effects and far less time in hospital.

IMRT and IGRT shape the radiation beam to the tumour's outline from multiple angles and check the patient's position with a scan before every session, so surrounding organs receive less dose. Fewer, larger doses are now standard in breast and prostate cancer, but a low-dose bath still spreads across normal tissue.

Measuring the dose the patient actually receives, with detectors on the skin or the imaging panel behind them, to catch errors before they cause harm.

The scanners built into or beside the radiotherapy machine that photograph the patient seconds before the beam fires, so the tumour is where the plan expects and, on the newest machines, so the plan can be redrawn to that day's anatomy.

Giving a single large dose of radiation directly to the tumour bed during surgery, with normal organs moved out of the way; used mainly in breast cancer as an alternative to weeks of external radiotherapy.

Software that learns from hundreds of past plans what dose distribution is achievable for a new patient, and produces a plan in minutes that a planner would have taken hours to reach.

Lattice radiotherapy deliberately treats a bulky tumour unevenly, placing peaks of tumour-destroying dose at spaced points inside it while the tissue between receives far less, relying on bystander and immune effects to extend the kill. It runs on standard linear accelerators, but evidence is mostly palliative and single-arm, and the mechanism is unsettled.

Radiotherapy machines are built by a very small number of companies. Two of them make most of the world's linear accelerators, a handful build proton systems, and installing, commissioning and servicing a machine is as much a part of the supply chain as building it.

Dozens of rice-grain-sized radioactive seeds are implanted permanently in the prostate in a single procedure and deliver their dose over months.

Magnetic nanoparticle hyperthermia injects iron-oxide nanoparticles into a tumour and heats them from outside with an alternating magnetic field.

An MR-linac is a radiation machine with an MRI scanner built in, so images taken during setup let the plan be re-optimised in minutes to that day's anatomy. It allows tighter margins and higher doses in pancreatic and prostate cancer, but treatment is slow and costly, and whether daily adaptation improves cure rates rather than only toxicity is unproven.

The software that holds a radiotherapy patient's plan, checks that the machine settings match it before every beam is switched on, and keeps the record of every dose given. Almost every department runs one of two systems.

Short courses of radiation, often a single treatment, to relieve pain from bone metastases, stop bleeding, open blocked airways or protect the spinal cord. Among the most cost-effective treatments in cancer.

Cameras that watch the patient's skin in three dimensions, robotic couches and moulded shells that hold the body still, so each radiotherapy dose lands where the plan says without tattoos and with the beam paused if the patient moves.

Modern proton machines paint the tumour spot by spot with a magnetically steered pencil beam, so the dose can be shaped in three dimensions and the proton's stop-point is put to full use.

Shining low-power red or near-infrared light on the inside of the mouth before and during treatment prevents severe mouth ulcers in people having head and neck radiotherapy or high-dose chemotherapy for transplant. Mucositis guidelines recommend it, though few centres yet have the equipment.

Probiotic supplements (Lactobacillus, Bifidobacterium) may reduce diarrhoea during pelvic radiotherapy for cervical, rectal and prostate cancer and some chemotherapy, but a 2018 Cochrane review rated the evidence low certainty and strains differ between trials. Patients in profound neutropenia or with a central line should not take them without advice, because bloodstream infections have occurred.

Small-cell lung cancer spreads to the brain so often that doctors used to irradiate the whole brain pre-emptively. Regular MRI scans are now challenging that practice.

Rotating the proton beam continuously around the patient instead of firing from a few fixed angles, to spread the entrance dose and sharpen the target dose.

Radiation using protons, which stop inside the tumour instead of passing through, so tissue behind it gets no dose.

Proton centres are built around one of three accelerators, a cyclotron, a synchrotron or a compact synchrocyclotron, feeding one or several treatment rooms through magnets and a rotating gantry the size of a house. Single-room systems have cut the price of entry, and upright treatment chairs may shrink the building again.

Nanoparticles that turn ordinary radiotherapy X-rays into a much bigger dose exactly where they sit.

Millions of tiny radioactive glass or resin beads are injected into the liver artery, lodging in the tumour and irradiating it from within.

Using a tumour's gene expression or a patient's inherited variants to predict who needs more dose, who needs less, and who is at risk of severe side effects.

Using the thyroid's natural appetite for iodine to image and treat thyroid cancer with a radioactive form of it. The oldest theranostic, and now used more selectively than it was.

A drug that finds tumour cells and carries a radioactive atom that irradiates them from inside the body.

Drugs that shield healthy tissue from radiation: amifostine to protect salivary glands, palifermin for mouth ulcers, and newer agents aimed at the gut, lung and skin.

Drugs given with radiotherapy to make tumour cells easier to kill: cisplatin in cervical and head and neck cancer, temozolomide in glioblastoma, nimorazole for hypoxic tumours, and a new generation aimed at DNA repair.

About half the people who need radiotherapy will need it as part of curing their cancer, yet many countries have one machine per several million people or none at all. Closing the gap is one of the highest-return investments in cancer care.

The measuring instruments that prove a radiotherapy machine gives the dose it claims: ionisation chambers, detector arrays, water tanks and plastic stand-in patients, checked every day, month and year and before every complex plan is delivered.

The software that calculates exactly how radiation beams should be shaped and checks the machine delivered it.

The machine that makes modern brachytherapy safe for staff: a shielded safe holding one tiny, intensely radioactive source on a cable, which it drives out through tubes into applicators inside the patient, dwells at programmed positions, and pulls back before anyone re-enters the room.

Hardware that copes with tumours that move when the patient breathes: belts and cameras that switch the beam on only in part of the breathing cycle, devices that hold the breath, and implanted beacons or X-ray tracking that let the beam follow the tumour.

Ways of dealing with tumours that move as the patient breathes: image the motion, treat only in part of the breathing cycle, hold the breath, or chase the tumour with the beam.

A radiotherapy machine built like a CT scanner: the accelerator spins inside an enclosed ring, must image the patient before every dose, and treats fast. Ethos adds software that redraws the plan to the anatomy of the day while the patient lies on the couch.

Stereotactic body radiotherapy converges multiple beams with sub-millimetre accuracy to deliver tumour-destroying doses in one to five outpatient sessions, doing the job of surgery for inoperable early lung cancer and for metastases in liver, spine and brain. Tumour size and location limit its use, and late toxicity is a concern near the central airways.

A bare scalp burns in sun it has never met, loses heat fast in cold, and is more easily irritated while treatment is going on. The measures are small and free, and they are the part of hair loss a person can act on from the first week.

Skin reactions in the treated area peak around the end of radiotherapy and heal. A thin silicone film applied from the first day cut moderate or severe reactions from 45.6 to 15.5 per cent in a randomised trial in breast cancer, and an international guideline recommends it. Permanent changes, such as fine broken veins and firmness, come later and do not reverse.

A drug that does nothing until ultrasound hits it, then kills the cells that took it up. Being tested in brain tumours because sound reaches where light cannot.

Treating every visible metastasis with ablative doses when there are only a few, on the idea that some patients with limited spread can still be controlled or cured.

A single very high dose, or a few doses, aimed at a small brain or spine target with millimetre precision, replacing whole-brain radiotherapy for most brain metastases.

Low-energy X-rays that stop within a few millimetres, used to cure basal and squamous cell skin cancers where surgery would scar or is not wanted.

Cameras track the patient's skin surface in three dimensions during treatment, replacing tattoos and pausing the beam if the patient moves.

Keeping food going down the throat during radiotherapy, and doing swallowing exercises through it, both independently predict being back on a normal diet afterwards. In 595 patients, those who kept eating were twice as likely to be on solid food at three to six months and those who exercised were 2.9 times as likely.

The equation radiotherapy uses to compare schedules: cell kill has a part proportional to dose and a part proportional to dose squared, and the ratio between them (alpha over beta) tells you how much a tissue cares about the size of each fraction.

Radiotherapy delivered the way a CT scan is taken: a small accelerator circles the patient while the couch slides through, painting the dose slice by slice with a fast shutter-like collimator. It handles very long or oddly shaped targets and images the patient with the same beam before each session.

Irradiating the whole body, or just the bones and marrow, to wipe out the patient's blood system and immune cells before a stem cell transplant.

A low-energy electron beam treats the entire skin surface, for lymphomas that live in the skin, without penetrating to the organs beneath.

Cells short of oxygen are up to three times harder to kill with radiation. Finding hypoxic tumours and fixing the shortage, with drugs, breathing gases or dose escalation, is one of radiobiology's oldest ideas and still unfinished business.

VHEE radiotherapy fires electrons at 100 to 250 MeV, energies that reach deep tumours and can be steered by magnets, aiming to deliver FLASH-speed radiation from a machine smaller and cheaper than a proton facility. It is still at the accelerator-development and preclinical stage: no patient had been treated by September 2026.

The linac sweeps around the patient in one or two arcs while the beam shape, dose rate and speed all change, delivering an IMRT-quality plan in a couple of minutes.

A self-shielded brain radiosurgery machine: a compact accelerator swings around the head on two nested gantries inside its own steel shell, so it needs no concrete bunker and no radioactive cobalt, and can be installed in an ordinary outpatient building.