Radiotherapy: How Is Radiation Treatment Planned?

What is it?

Radiotherapy is the directing of high-energy radiation at the tumour area. The radiation damages the DNA of cells. Cancer cells may not repair this damage as well as healthy cells. Treatment is most often given from outside with a device called a linear accelerator.

This procedure is planned and carried out by the radiation oncologist. The medical oncologist decides together at the tumour board whether the drug should coincide with radiation. The medical oncologist does not deliver the radiation personally. The number of sessions and the total dose are calculated according to the tumour type and the tolerance of the surrounding organ.

How does it work?

The dose is calculated at the limit that will affect the tumour but that the surrounding organ can tolerate. The target is drawn on the images and the surrounding tissues are protected. Intensity-modulated and image-guided techniques make this calculation more precise.

In some regimens the radiation is given in small daily doses over several weeks. Stereotactic body radiotherapy delivers a high dose to a narrow area in a small number of sessions. Brachytherapy, given from inside, is a separate method in which the source is placed in a body cavity or tissue.

In which cancers is it used?

Breast, lung, prostate, head and neck, rectum, gynaecological tumours and many brain metastases are frequent examples. It can be used to shrink the tumour before surgery, to irradiate the tumour bed after surgery, or to achieve control in disease that cannot be operated on.

Palliative radiation with shorter regimens is also given for symptoms such as bone pain or bleeding. Which treatment is appropriate is discussed at the tumour board, with the relevant specialties taking part, by considering the type, stage and molecular features of the cancer and the person’s general condition together.

How is it given?

There is first a simulation session: the person is laid in the treatment position, a mould that keeps the body still may be prepared, and a computed tomography scan is taken. The actual sessions follow this plan and on most days last a few minutes. No pain is felt during the radiation.

Skin marks or small tattoo points may be used to keep the position. If chemotherapy will fall in the same weeks, the blood count is shared between the two teams.

During follow-up, blood tests, imaging and symptom review are read together. The dose or date may be changed according to side effects and organ function. The list of medicines used at home is updated at every visit. Sudden fever, shortness of breath, uncontrolled diarrhoea or bleeding should be reported the same day.

Possible side effects

Fatigue and redness of the irradiated skin are common. Depending on the area, difficulty swallowing, diarrhoea, urinary complaints or dry mouth may be added. Most side effects fade within weeks after treatment ends. Some organ effects can appear later.

Fever, shortness of breath or pain that does not pass should be reported to radiation oncology and medical oncology. Products applied to the skin should be approved by the team.