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What is radiation therapy?
Radiation therapy (radiotherapy) constitutes the third pillar of modern cancer therapy besides surgery and chemotherapy. The treatment with ionising radiation keeps tumours under control or destroys them. In many cases, so-called multimodal therapy approaches are used. These approaches combine various treatment options. The surgical removal of a tumour, for example, can be followed by a combined radiochemotherapy (radiation therapy combined with chemotherapy). Some benign diseases can be treated with radiation therapy as well. This, however, is only of minor importance in modern medicine.
Mechanism of action
Ionising radiation causes damage to the genetic material of the exposed cells and can thus prevent cell division and kill off cells. The repair mechanisms inherent to healthy tissue can eliminate the damage caused to the genetic information. In cancer cells, the capacity of these mechanisms is often limited. This explains why many malignant tumours are particularly sensitive to ionising radiation.
In radiation therapy, a high radiation dose is irradiated onto a limited narrow area, the so-called target volume (consisting of the tumour and its spread area). The aim is to destroy the tumour. At the same time, adjacent radiation-sensitive organs and tissues (so-called organs at risk) should be spared.
Radiotherapy treatment planning
The challenge in radiation therapy is to hit the area to be treated as precisely as possible while protecting surrounding healthy organs and tissues. For this to be achieved, the tumour has to be localised accurately. As part of radiotherapy treatment planning, the area to be irradiated (target volume) and the radiotherapy technique are determined. Modern radiotherapy techniques allow limiting the radiation dose to the target volume contoured beforehand.
Fractionated radiotherapy - radiation in small fractions
In order to avoid side effects, the radiation dose is usually not administered in one session but in several small fractions. In this way, healthy tissue can recover between the individual radiation treatment sessions. Damage caused to the genetic material can be repaired again. Patients usually undergo radiotherapy five days a week, with the remaining two days as treatment-free days (mostly at the weekends).
Fractionated radiotherapy is better tolerated by patients but often results in a longer duration of therapy lasting several weeks.
Despite all caution, side effects from radiation therapy cannot be completely avoided. As radiation therapy is a kind of local treatment, also the side effects are limited to the treated area.
The side effects are diverse and can basically affect all organs and tissues exposed to radiation. During therapy, for example, irritation of the skin and mucous membranes often occurs in the exposed area and usually subsides quickly after radiation therapy has ended.
Other radiation-induced side effects such as chronic inflammations, tissue induration (fibrosis) and shrinkage, in some cases, occur only long after radiation therapy. Possible late effects of radiation therapy also include the emergence of secondary cancers (often many years later).
As every radiation therapy may lead to side effects, the benefits of the therapy and the risk for the patient have to be balanced beforehand by the attending physician. Before and also during treatment the patient is protected from a too high dose of radiation by various measures.
State of 2018.07.31