Radiation therapy is an old German term for the treatment of malignant (malignant) or benign (benign) diseases within radiology. Since 1988, radiotherapy has branched off from radiology in Germany to form an independent specialty. The terms radiotherapy and radiation oncology are often used interchangeably, with radiation oncology usually implying more comprehensive care of tumor patients. In oncology, surgery, chemotherapy and radiotherapy form three important pillars of efficient tumor treatment. Close interdisciplinary cooperation between these sub-areas is essential, so that nowadays radiotherapy is usually incorporated into a tumor center with surgeons, oncopathologists, radiologists, psychooncologists, etc. In principle, radiotherapy, like surgery, is a local treatment method whose effect is limited exclusively to the site of application. It is based on the interaction of ionizing radiation with biological structures. Statistically, about two-thirds of all localized tumors are cured today, with surgery accounting for one-third and radiotherapy for one-third. In addition, radiotherapy makes a critical contribution in the size reduction of tumors for symptom relief or before surgical removal of the tumor.
Radiation therapy strategies
Depending on tumor type, tumor extent, and the patient’s general health, a therapeutic goal is set before the start of each radiotherapy session, and a general distinction can be made between curative and palliative approaches.
- Curative therapy: based on the pretherapeutic diagnosis, there is a realistic chance of cure, so therapy is directed toward a cure.
- Radiotherapy alone: in the case of sufficiently radiosensitive tumors, surgical removal of the tumor may be omitted and radiotherapy alone performed, given the same chance of cure as well as the desire for a better functional or cosmetic outcome (examples: malignant lymphomas, some brain tumors, prostate carcinomas, anal carcinomas).
- Neoadjuvant (preoperative) radiotherapy: radiotherapy is given before surgery with the aim of tumor shrinkage, destruction of tumor extensions that have already penetrated the surrounding area, or devitalization of tumor cells to reduce the risk of intraoperative cell spread.
- Adjuvant (postoperative) radiotherapy: radiotherapy is given after surgery to kill tumor remnants that may not have been removed, thus preventing recurrence.
- Consolidating radiotherapy: radiotherapy is given after primary systemic chemotherapy to stabilize a complete remission achieved by chemotherapy.
- Palliative therapy: in the case of advanced tumors, no cure is expected. However, radiotherapy is a very important tool to improve the quality of life and maintain the patient largely symptom-free.
- Stabilization radiation: radiation is administered at about two-thirds of the tumor-destroying dose and is indicated, for example, in cases of instability due to skeletal metastases or neurological deficits in brain metastases.
- Pain radiation: tumor-related pain can often be relieved by radiation, so that painkillers can be saved to a large extent. The radiation dose is often only a quarter to a third of the tumor destruction dose.
Organization of radiation oncology
Radiation therapy can be performed in radiation hospitals, radiation therapy departments, or private practice radiation oncology units. In a large hospital, the radiation clinic usually consists of three areas:
- Polyclinic: patient admission, tumor follow-up, examination and therapy rooms, pastoral care, etc.
- Bed department: standard occupancy, day beds, etc.
- Therapy Department: the therapy department is the basis of the radiation clinic and consists of two areas:
- Radiation planning: cross-sectional imaging equipment for tumor localization (CT, MRI, sonography), radiation planning systems.
- Therapy: linear accelerator, X-ray therapy, brachytherapy, hyperthermia, etc.
In addition to a medical-medical area of competence, there is also a physical-technical area in a radiation clinic, which is the responsibility of physicists and makes a decisive contribution to the correct technical implementation of therapy.
Radiation Biology
The cells of the human organism are the smallest independently functioning units. They consist of a nucleus containing the genetic material (DNA), the cytoplasm, and membranes. Complex regulatory processes control the cell cycle, cell division and all necessary cell functions. In principle, tumor cells do not differ from normal cells. However, their cell cycle is disturbed by various DNA mutations (activation of oncogenes or inactivation of tumor suppressor proteins), usually resulting in unstoppable cell division and uncontrolled tumor growth. The main target of ionizing radiation is the genetic material (DNA). Irradiation causes hydrogen bond breaks, base damage, strand breaks, DNA cross-links or bulky lesions (multiple damage, often irreparable) on the DNA. The consequence of DNA damage is inhibition of proliferation of cells, which eventually leads to cell death. Local irradiation of a tumor is expected to damage the DNA and thus inactivate the tumor cells, so that the tumor is inhibited in its growth or destroyed by cell death. Since healthy body cells are also damaged by radiotherapy, special care must be taken to protect the surrounding tissue.
Radiation therapy methods
Depending on the localization of the radiation source, a distinction is made between the following therapeutic principles:
- Teletherapy (percutaneous radiotherapy): the radiation source is located outside the body, and the focus-to-skin distance is more than 10 cm. Teletherapy includes:
- X-ray therapy
- Telegam therapy
- High energy therapy
- Brachytherapy (short-distance therapy): radiation is delivered at close range, the distance between the target volume and the radiation source is less than 10 cm. Brachytherapy includes:
- Contact therapy: the radiation source has direct contact with the patient (e.g., skin, eyeball, intraoperative radiotherapy).
- Intracavitary therapy: the radiation source is introduced into a body cavity (e.g., uterine cavity, vagina, bladder, esophagus/esophagus).
- Interstitial therapy: the radiation source is implanted directly into the tumor tissue.
Furthermore, there are numerous parameters that must be individually selected prior to the implementation of radiotherapy depending on tumor localization and tumor histology. These include, for example:
- Radiation type
- Field size
- Field boundary
- Focus skin distance
- Filtering
- Body inhomogeneities
Overall, radiotherapeutic methods are very diverse and always adapted to the individual conditions of the patient. Indispensable is a competent cooperation between physicists, physicians and MTRA (medical-technical radiology assistants). The main goal is maximum tumor cell damage with maximum tissue protection. Individual radiation concepts have already been established for each organ or tumor type.