Colorectal cancer – Radiotherapy

Radiation therapy (also known as radiotherapy) is used for colorectal cancer at various stages of the disease, usually in conjunction with surgery and medical oncology, to achieve a cure (curative radiotherapy). Radiation therapy focuses high-energy X-rays on the tumor inside the body to specifically kill it. As a rule, we mainly treat rectal cancer (also known as rectal carcinoma) in this situation.


Radiotherapy can also be used if the bowel cancer has already spread: radiotherapy can then prevent or alleviate symptoms caused by metastases, e.g. in the brain or bones(palliative radiotherapy).

Radiation therapy is performed as an outpatient treatment, is non-invasive (i.e. does not require anesthesia) and can thus be easily integrated into everyday private and professional life. Depending on the extent of the tumor, radiotherapy can be carried out in one or a few treatment sessions as radiosurgery for small tumor foci, or as fractionated treatment over several weeks for larger tumors. Radiation therapy is often combined with chemotherapy or immunotherapy to improve efficacy. Close and personal support is a matter of course for us.

The Department of Radiation Oncology at the USZ uses only the most modern techniques for precise and low side-effect radiation treatment of bladder cancer. You will be looked after by proven experts in the treatment of colorectal cancer.

For many patients, we are already offering the treatment of tomorrow: in clinical trials, we are continuously working on improving the treatment of perineal cancer to make it even more effective and tolerable. To the overview of currently open studies.

In the following, we will describe the radiotherapies for different types and stages of colorectal cancer:

Locally advanced rectal cancer in the operable stage

In early-stage rectal cancer, surgical removal of the tumor is the treatment of first choice for fit patients.

In the case of larger tumors, or if there are already metastases in the lymph nodes, the operation is supplemented by radiotherapy and usually also chemotherapy. This reduces the risk of recurrence in the future, improves the chance of recovery and simplifies the removal of the tumor.

Depending on the stage of the tumor and the patient’s general condition, chemotherapy is also given alongside radiotherapy to eliminate any disseminated cancer cells and make the cancer cells more sensitive to radiation. As a rule, this is a tablet chemotherapy. The combination of surgery, radiotherapy and chemotherapy as so-called “trimodal therapy” then offers the greatest chances of recovery.

Due to the often extensive treatment area, the radiation is divided into many small “portions”: the therapy is fractionated over approximately 28 treatment sessions per working day over a period of around 6 weeks. Spreading the radiation treatment over several weeks improves the tolerability of the treatment, which is mainly carried out on an outpatient basis and can be easily integrated into the patient’s private and professional life. It goes without saying that patients receive close medical and nursing care during this time in order to provide the best possible support for illness-related complaints.

In certain stages and depending on the patient’s general condition, a shorter course of treatment can be used as an alternative to the several weeks of radiotherapy described above. This involves treatment with a higher-dose radiotherapy in 5 sessions and also before the operation. In this case, chemotherapy is not given in parallel. In both cases, examinations are carried out again 6 weeks after the end of radiotherapy to assess the response. The operation is then planned.

Radiotherapy for colorectal cancer is a clinical focus of our clinic. State-of-the-art equipment and experienced medical physicists and MTRAs contribute to treatment of optimum quality and safety. At the same time, we work closely with our colleagues in surgery and medical oncology in order to guarantee treatment “from a single source”. This is already guaranteed by the Interdisciplinary Consultation Hour of the Colorectal Center, which takes place before the start of treatment, where you can be advised by doctors from Visceral Surgery, Medical Oncology and Radio-Oncology at the same time.

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Organ preservation in rectal cancer

If the tumor is located in the lower rectum near the sphincter muscle, patients may opt for treatment without surgery in order to preserve sphincter function. Studies in recent years have shown that patients in whom the tumor completely regresses after radiation and chemotherapy may not require surgery and can therefore retain their rectum and sphincter function.

This treatment has been in use for around ten years, but there is still a lack of longer-term observational data. Taking into account the current guidelines, we can offer you such a waiver of the operation after personal and individual clarification. Both in the initial consultation and in the interdisciplinary consultation after the follow-up examinations (6 weeks after radiotherapy), we as an interdisciplinary team will assess which options are suitable for you.

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Metastases of colorectal cancer, e.g. in the brain or bones

Colorectal cancer is an aggressive type of cancer that often forms metastases during the course of the disease: this is called metastasis. Common sites of metastasis are the lung, adrenal gland, bones, liver or brain. Radiotherapy is a highly effective method with few side effects to prevent or treat symptoms caused by metastases. This is usually done in combination with chemotherapy, immunotherapy or other targeted therapy. The smaller the metastases are and the earlier they are irradiated, the better the results. Today, metastases in the body can be treated in a focused manner in just a few effective radiation sessions.

For tumor foci in the abdominal area, e.g. liver or upper abdomen, we carry out body stereotactic radiotherapy (SBRT) on our MRI hybrid accelerator. State-of-the-art radiation technology is combined with MRI images. The radiation is thus carried out under MRI monitoring of the tumor, so that the highest precision is combined with the best imaging. Our clinic was the first in Switzerland to introduce this technology back in 2019. We are still the only clinic in German-speaking Switzerland to offer the highest level of expertise in this field.

Today, brain metastases are treated at our center for most patients by means of a single high-dose radiation treatment: this is called radiosurgery. Metastases at other locations in the body can now also be treated in a focused manner in just a few effective radiation sessions. Metastatic colorectal cancer is a clinical and scientific focus of our clinic. We pass on our knowledge in a large number of international courses and congresses. We are active as international experts in guideline commissions.

State-of-the-art equipment and experienced medical physicists and MTRAs contribute to treatment of optimum quality and safety. At the same time, we work closely with our colleagues in medical oncology to guarantee “one-stop” treatment. We also consult with our colleagues in palliative medicine at an early stage.

In clinical trials, we are continuously trying to improve the treatment of colorectal cancer in order to make it even more effective and tolerable. To the overview of currently open studies.

Responsible doctors

Claudia Linsenmeier, Dr. med.

Attending Physician with extended responsibilites, Department of Radiation Oncology

Tel. +41 44 255 26 73
Specialties: Focus on breast/gynecology, Gastro-Intestinal Radio-Oncology, Pediatric radio-oncology

Eugenia Vlaskou Badra, Dr. med.

Attending Physician, Department of Radiation Oncology

Tel. +41 44 255 35 66

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