Radiation Oncology

Intensity modulated radiotherapy (IMRT) is especially suitable for tumors with a complex 3-dimensional morphology located in the vicinity of radiosensitive organs. Multiple radiation fields coming from different directions and with individually modulated intensities converge in the tumor (target volume) forming “dose topographies”. The overlap of all these dose structures results in an even dose distribution in the complex shape of the target volume, while carefully protecting the adjacent radiosensitive organs. The modulation of the intensity of each individual radiation field is achieved by the movable and automatically controlled leaves of the multi-leaf collimator (MLC) within the accelerator. With the aid of powerful computers the expert team of medical physicists determines the highly complex sequence needed for each patient and treatment plan, which is then validated by extensive measurements at the linear accelerator.

Image Guided Radiotherapy (IGRT) combines imaging and radiotherapy in the same irradiation unit. This allows the reproducible and precise positioning of patient and target volume at the beginning and during the radiation treatment. At the same time 3-dimensional imaging permits the radiotherapist to react immediately to anatomical changes of patient and tumor.

Here at the Medical Center – University of Freiburg we perform intraoperative radiotherapy (IORT) either with the mobile Intrabeam system by Carl Zeiss AG or with the Mobetron linear accelerator by MD51, directly in the operating room.

During IORT the radiotherapist, the surgeon and the medical physicist work very closely together. In contrast to other radiation methods, healthy organs can be moved out of the radiation beam and intraoperative findings can directly influence the extent of the radiotherapy.

The Intrabeam system generates low energy X-rays, which are most effective at close range. With a spherical applicator the tumor bed, or resection cavity, can be directly irradiated.

The Mobetron system is a mobile linear accelerator using electron radiation. This provides careful control of radiation penetration depth, helping to protect healthy organs. The mobility of the device is suitable for adapting radiation to the individual case.

These specialized mobile units enable us to provide optimum protection of healthy tissue. The devices can be utilized for a wide range of surgical interventions, e.g. in senology (breast cancer), gynecology, and urology, as well as abdominal, plastic and thoracic surgery.

Intraoperative Radiotherapy in Breast Cancer

• New treatment improves chances of recovery
• Optimal protection of healthy tissue
• Shorter duration of treatment

Breast cancer is the most common form of cancer in women. In recent years, a new breast-conserving treatment has gained importance: intraoperative radiotherapy (IORT). The Department of Gynecology and Obstetrics of the University Medical Center Freiburg (Director Prof. Dr. Dr. h. c. G. Gitsch) together with the Department of Radiation Oncology (Director Prof. Dr. med. A.L. Grosu) implement this innovative and beneficial method with the Intrabeam radiotherapy system built by Carl Zeiss AG, Germany. Prof. Dr. Anca-Ligia Grosu emphasizes the high radiation dose that can be applied directly in the tumor region with IORT. The radiotherapist and the surgeon collaborate closely during the procedure. According to Dr. T. Erbes, Head of the Senology Unit of the Department of Gynecology and Obstetrics, IORT offers a very precise way to treat the tumor bed, where there is the greatest risk of cancer recurrence, while still in surgery. The soft X-rays are most effective at close range. Thus adjacent organs, which are beyond the radiation field, can be protected from exposure to radiation while still maintaining a high radiation dose in the tumor bed.

Last but not least, the combination of IORT and conventional radiotherapy of the whole breast results in a much shorter duration of treatment.

Brachytherapy is a form of radiotherapy where a sealed radiation source is placed inside or next to the area requiring treatment.

In certain cases the artificial overheating of tumors by electromagnetic waves (interstitial hyperthermia) can enhance the effect of radiotherapy and chemotherapy.

Since December 2023, the Department of Radiation Oncology, Medical Center - University of Freiburg, offers the possibility to continuously adapt the treatment to the daily changes in the patient's body (online adaptive radiotherapy, oART).

The goal of online adaptive radiotherapy is to adapt the patient's treatment plan to the current anatomy in order to account for differences due to organ movement and organ filling between fractions prior to daily treatment. This is made possible by the latest generation of linear accelerators – Ethos with the integrated online 3D imaging system HyperSight^TM by Varian Medical Systems. HyperSight^TM  is the fastest CBCT imaging available and provides the best image quality for oART.

Radiotherapy (Radiation oncology/Radiation therapy) is concerned with the medical application of ionising radiation. The aim of which is to treat disease - in particular malignant but also benign - , to delay its progression or relieve discomfort. In addition to surgery and medication, radiotherapy plays an important role in the treatment of cancer. In this respect it may be employed alone, prior to, during or after surgery.

Moreover it is possible to combine radiotherapy with tumouricidal pharmaceuticals (chemotherapy). It is possible to administer a chemotherapy or immunotherapy pharmaceutical that increases the tumour's sensitivity to radiation. To better protect healthy tissue radio-protective substances can also be administered. The correct treatment combination is dependent on the case and is defined in an individual treatment concept specific to the patient. Depending on the type of cancer radiotherapy is used in either a curative or palliative setting. In the case of a curative therapy the aim is to completely destroy the tumour. If this can be achieved then the patient is cured. It can also be sensible to preventatively irradiate after surgery, in order to destroy malignant cells which may remain at the surgical site. If cure of a particular cancer is no longer possible, for example if it has already metastasized, palliative radiotherapy is employed to relieve, or even eradicate, symptoms such as pain, shortness of breath, bleeding and paralysis. The well-being and quality of life of the patient would, thereby, be greatly improved.

Mode of operation

Radiotherapy uses radiation to transmit energy that will disrupt the growth of cells in the irradiated tissue. More precisely: Radiation therapy damages the genetic material (DNA) within the cell nucleus, thereby inhibiting cell division. While healthy cells can repair the damages, tumor cells are less adaptive: They are stopped in their growth, or even destroyed.

The required dose of radiation – measured in “Gray” (Gy), an international unit named after physicist Louis Harold Gray – depends on the radiation sensitivity and the position of the tumor. The treatment plan determines for each individual patient the dosage and fractionation, i.e. the number of “single portions” for delivering the required dose. The plan must also consider the possible irradiation of healthy tissue and organs encountered by the radiation beam on its way to the tumor.

Usually the total dose is divided into several radiation sessions, or fractions. Typically fractions of 1.8 to 2.0 Gy are applied. Healthy cells need a certain amount of time to recover from radiation effects. If the next fraction is delivered after completion of this “repair work”, the patient tolerates the treatment better and has fewer side effects. Therefore radiotherapy may stretch over several weeks.

Special situations, however, in particular with high-precision radiotherapy, may provide indication of higher single doses up to 20 Gy. This is possible when such a small amount of healthy tissue is irradiated that – as in surgery – “scarring” of the affected area becomes acceptable.