Selective internal radiotherapy (SIRT, also known as transarterial radioembolization) is a form of local radiotherapy. It is used for cancers of the liver. Radioactive particles are introduced into the liver via special microspheres (SIR spheres). There they irradiate the diseased tissue in a targeted manner.
You can find further information and selected SIRT specialists here.
Liver cancer refers to the uncontrolled growth of cells within the liver. A distinction is made between
In Germany, around 6000 people are diagnosed with primary liver cancer every year. However, liver metastases are much more common: every year, around 30,000 patients affected by colorectal cancer are found to have metastases in the liver.
Several studies have shown that selective internal radiotherapy (SIRT) can greatly reduce the size of liver tumors. In some cases, the tumor can be reduced to such an extent that subsequent surgical removal is possible. In individual cases, the tumor can even be completely destroyed by radiation.
SIRT can also improve the quality of life and life expectancy of patients whose cancer does not respond to chemotherapy.
Selective internal radiotherapy is used for
However, SIRT is only possible if the liver is still functioning well. Liver function is checked with a blood test before SIRT therapy.
Careful examinations are necessary before SIRT. They are intended to ensure that the radioactive microspheres used in SIRT are used safely on the patient. For this purpose, a doctor assesses the blood vessels in the liver.
An important instrument for these preparations is an inguinal catheter. It is advanced into the liver as part of an angiography.
The doctor then uses the catheter to close the adjacent blood vessels leading from the liver to other organs of the body with metal coils. This process is called embolization. This closure ensures that the radioactive microspheres act exclusively in the liver and do not reach other body organs via the bloodstream.
In addition, the doctor injects a low-level radioactive substance into the blood vessel via the catheter. He then checks the distribution of the radioactivity on the scintigraph (device for displaying the results of the nuclear medicine examination method).
This also enables the doctor to individually determine the radiation dose required later for the SIRT.
The preparatory examination can be carried out on an outpatient or day-care basis. If there are no objections to SIRT as a result of this preliminary examination, it can be carried out after around one to two weeks.
In SIRT, radioactive microspheres are introduced directly into the tumor and can thus irradiate it at close range © Henrie | AdobeStock
Healthy liver tissue is mainly supplied with nutrients via the portal vein(vena portae). The hepaticartery (arteria hepatica), on the other hand, plays only a minor role in supplying the liver. A cancerous tumor, on the other hand, receives its blood primarily via the hepatic artery.
SIRT makes use of this difference in blood supply by inserting radioactively charged microspheres - so-called microspheres made of glass or resin - into the hepatic artery via a catheter in the groin. The microspheres contain a radioactive isotope (atom, in this case yttrium-90), which only has a short radiation range of two to eleven millimeters.
These spheres penetrate directly to the cancerous tumor and are deposited in the smallest blood vessels within the tumor. In this way, they expose the cancer cells there to a high dose of radiation, while healthy tissue is largely spared.
At the same time, the blood vessels that supply the tumor with nutrients are sealed off, effectively "starving" the cancer cells. The treatment usually reduces the size of the cancerous tumor, in a few cases it is even completely destroyed.
The procedure usually takes about an hour and a half and is performed under local anesthesia.
Abdominal pain and nausea may occur during the treatment. The patient is therefore given anti-nausea medication and a painkiller via the vein as a preventative measure. After SIRT treatment, patients are regularly examined with blood tests and radiological procedures to monitor the success of the therapy.
Patients usually tolerate SIRT well. It is particularly gentle compared to chemotherapy or external radiation therapy. So far, no hair loss (alopecia) has been observed following SIRT treatment.
The radioactive particles used in the treatment only reach a few millimeters and do not penetrate any other body organs. Accordingly, there is no radiation exposure for the person undergoing treatment.
Nevertheless, as with any therapy, undesirable consequences can occur. Angiography can lead to side effects and complications such as
may occur. In addition, a so-called post-embolization syndrome may occur due to the vascular occlusion and rapid decay of the cancer cells (within one to five days). This results in flu-like symptoms such as
Accidental storage of microspheres outside the liver can, due to the radioactive radiation, lead to
ulcer.
In very rare cases, the following can occur after SIRT
to.
Allergic reactions to the microspheres have not been observed to date.
On the first day after the procedure, the distribution of the microspheres is precisely documented using a scintigraph. This enables doctors to detect deposits outside the liver at an early stage.
As a rule, patients stay in the clinic for one to two days. This allows the clinic team to intervene immediately in the event of any complications.
Aftercare also includes regular checks on liver function and the success of the treatment using imaging procedures such as
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