Rather than focusing only on treating cancer throughout the body, therapies such as Selective Internal Radiation Therapy (SIRT) aim to deliver radiation directly to a liver tumour while limiting unnecessary exposure to surrounding healthy tissue.

SIRT, also known as radioembolisation, is a specialised form of internal radiation therapy. It uses millions of tiny microspheres containing the radioisotope Yttrium-90 (Y-90). These microspheres are introduced into the blood supply of a liver tumour, where they become lodged in the small blood vessels supplying the tumour and release radiation directly around the cancerous tissue.

SIRT may be considered for people with primary liver cancer or cancer that has spread to the liver (metastatic liver cancer) when surgical removal is not appropriate. Like all cancer treatments, SIRT requires a careful balance between potential benefits and possible risks.

Learn how Selective Internal Radiation Therapy (SIRT) targets liver cancer using radioactive microspheres. Understand treatment benefits, eligibility, and expert care from the best liver transplant surgeon in India.

Several factors must be considered, including the type and extent of the tumour, liver function, overall health, previous treatments and the anatomy of the patient’s blood vessels.

This article provides a general overview of Selective Internal Radiation Therapy (SIRT), including how it works, who may be eligible, the treatment process, potential benefits and its relationship with liver transplantation.

1. What Is Selective Internal Radiation Therapy (SIRT)?

Selective Internal Radiation Therapy (SIRT) is a targeted treatment used for selected liver tumours. It is performed by an interventional radiologist, who uses imaging guidance to deliver radioactive microspheres directly to the blood vessels supplying a liver tumour.

The doctor guides a thin, flexible tube called a catheter through a blood vessel, usually in the wrist or groin, and advances it toward the blood vessels supplying the liver.

Once the catheter is positioned correctly, the radioactive microspheres are released.

Think of SIRT as sending millions of tiny packages directly to the neighbourhood where a tumour is growing. Each microsphere travels through the blood supply and becomes lodged in small vessels around the tumour. The microspheres then release radiation in the targeted area.

The goal is to expose the tumour to radiation while reducing radiation exposure to other parts of the body. However, some healthy liver tissue can also be affected, which is why careful patient selection and treatment planning are essential.

2. How Does SIRT Work?

Liver cancer can develop from the liver’s own cells, such as in hepatocellular carcinoma (HCC), or cancer from another part of the body can spread to the liver. This latter situation is known as metastatic liver cancer.

Liver tumours can sometimes involve several areas of the liver, making surgical removal difficult or inappropriate.

SIRT is used in selected cases of unresectable primary liver cancer and for certain metastatic cancers involving the liver when surgery is not suitable.

One of the important principles behind SIRT is the difference in blood supply between many liver tumours and normal liver tissue. The treatment uses the hepatic arterial blood supply as a pathway for delivering the microspheres.

The microspheres become trapped in the small blood vessels supplying the tumour and release radiation nearby.

The treatment can therefore be thought of as a targeted radiation delivery system. Instead of directing radiation from outside the body, SIRT delivers radioactive microspheres through the tumour’s blood supply.

3. What Is Yttrium-90 in SIRT?

The microspheres used in many SIRT treatments contain the radioactive isotope Yttrium-90 (Y-90).

Y-90 undergoes radioactive decay and releases beta particles, which are a form of radiation.

The radiation has a relatively short range in tissue. This makes Y-90 suitable for delivering radiation locally after the microspheres become lodged near the tumour.

The microspheres remain within the small blood vessels, while the radiation affects nearby tumour cells.

Because the radiation does not travel very far, the treatment is designed to concentrate its effect around the treated area. However, it is important to understand that healthy tissue may also receive some radiation, which is why treatment planning is so important.

4. Which Liver Cancers Can SIRT Treat?

SIRT may be used for several types of cancers affecting the liver.

These may include:

• Primary liver cancer, particularly hepatocellular carcinoma (HCC)
• Metastatic cancer involving the liver
• Colorectal cancer that has spread to the liver
• Selected neuroendocrine tumours that have spread to the liver
• Other selected secondary liver tumours

Whether SIRT is appropriate depends on the individual patient’s circumstances.

SIRT may be considered when a liver tumour cannot be safely removed by surgery or when other treatment approaches are not appropriate.

However, the use of SIRT does not necessarily mean that other treatments cannot be used later. Depending on the patient’s response and overall condition, additional treatment may be considered.

A multidisciplinary team may review imaging, laboratory results, liver function, tumour characteristics and overall health before recommending a treatment plan.

5. Who Is Eligible for SIRT?

SIRT is offered only to carefully selected patients.

Your medical team may consider several factors, including:

• The number, size and location of liver tumours
• The type of cancer
• The extent to which the cancer has spread
• Overall liver function
• Kidney function
• Blood cell counts
• Overall health
• The anatomy of the liver’s blood vessels
• Previous cancer treatments
• Whether the tumour can be removed surgically

SIRT may be considered for selected primary liver cancers when the liver is functioning sufficiently well and the tumour cannot be removed safely with surgery.

Importantly, one scan or one blood test does not determine whether someone is eligible for SIRT.

A multidisciplinary team may include an interventional radiologist, hepatologist, medical oncologist, surgical oncologist, hepatobiliary surgeon, radiation specialist and other healthcare professionals.

6. Who May Not Be Eligible for SIRT?

Not every patient with liver cancer is suitable for SIRT.

Potential reasons why SIRT may not be appropriate include:

• Severe liver dysfunction
• Certain patterns of cancer spread
• An unsuitable blood-vessel anatomy
• High risk of radioactive microspheres reaching other organs
• Certain conditions involving the portal vein or bile ducts
• Poor overall health that makes the procedure unsafe

Before SIRT, doctors carefully examine the liver’s blood vessels and tumour blood supply.

In some situations, doctors may block specific blood vessels to reduce the possibility of microspheres travelling to unintended organs.

This planning is extremely important. The treatment team needs to understand where the microspheres are likely to travel before radioactive treatment is delivered.

7. What Happens Before a SIRT Procedure?

Before treatment, several examinations and tests may be required.

Medical History and Previous Treatments

Your healthcare team will review your symptoms, previous cancer treatments, medications and other medical conditions.

Blood Tests

Blood tests may be performed to assess:

• Liver function
• Kidney function
• Blood cell counts
• Other factors relevant to treatment safety

CT or MRI Scans

Imaging such as a CT scan or MRI may be used to determine the number, size and location of liver tumours and to understand the extent of disease.

SIRT Treatment Planning

A separate planning procedure is usually performed before the actual radioactive treatment.

A catheter is inserted into an artery, commonly through the groin or wrist, and guided toward the blood vessels supplying the liver.

Contrast dye allows doctors to visualise the blood vessels.

A special radioactive tracer may then be administered to simulate how the treatment particles are likely to travel. Imaging is subsequently performed to evaluate the tracer distribution.

The information from this planning stage helps doctors determine whether SIRT can be performed safely and whether modifications to the blood vessels are required.

8. What Happens During the SIRT Procedure?

During the actual SIRT treatment, the patient is positioned in an interventional radiology treatment room.

Local anaesthetic is usually used to numb the area where the catheter will be inserted.

A thin catheter is then guided through an artery toward the blood vessels supplying the liver tumour.

Once the catheter is positioned correctly, the microspheres containing Yttrium-90 are carefully injected.

The microspheres travel through the blood supply and become lodged in the small vessels supplying the tumour.

The SIRT procedure commonly takes approximately one to two hours, although the exact duration can vary depending on the individual case and treatment complexity.

After treatment, the patient is monitored for a period of time. Depending on the treatment centre and the patient’s condition, an overnight stay may sometimes be required.

9. What Happens After SIRT?

After SIRT, some patients experience temporary side effects.

These may include:

• Tiredness
• Nausea
• Abdominal discomfort
• Reduced appetite
• Mild fever
• Diarrhoea
• Bruising or discomfort at the catheter insertion site

If diarrhoea occurs, maintaining adequate hydration is important to help replace lost fluids.

Your healthcare team will provide individual instructions regarding medicines, activity, diet, follow-up and any radiation-safety precautions.

Because SIRT involves radioactive material, patients may receive specific instructions about close contact with other people for a limited period. These instructions depend on the type of treatment and the regulations followed by the treatment centre.

10. What Are the Benefits of SIRT?

SIRT is designed as a targeted treatment for selected liver tumours.

Potential advantages include:

1. Targeted radiation:
Radioactive microspheres are delivered through the blood vessels supplying the tumour.

2. Localised treatment:
Radiation is concentrated in and around the treated liver tumour.

3. Reduced exposure to distant organs:
Because Y-90 radiation has a short range, radiation exposure outside the treatment area can be limited, although it cannot be eliminated completely.

4. Minimally invasive treatment:
SIRT is performed through a catheter rather than requiring major open surgery.

5. Option for selected unresectable tumours:
SIRT may provide a treatment option when surgical removal is not possible.

6. Potential combination with other treatments:
Depending on the patient’s condition, SIRT may form part of a broader liver cancer treatment strategy.

However, it is important to understand that SIRT is not a guaranteed cure for liver cancer. The goals of treatment can vary. In some patients, the aim may be to control tumour growth, reduce tumour burden, delay progression or relieve symptoms.

Patients with compromised liver function may also have a higher risk of treatment-related liver injury.

11. What Are the Possible Risks and Side Effects of SIRT?

Like every medical treatment, SIRT has potential risks.

Common short-term side effects can include:

• Fatigue
• Abdominal pain or discomfort
• Nausea
• Loss of appetite
• Fever
• Diarrhoea

There can also be less common but more serious complications.

If radioactive microspheres travel to unintended organs, they may cause injury to tissues such as the stomach or intestine. This is one reason why detailed blood-vessel mapping and treatment planning are performed before SIRT.

Another important concern is liver injury. Patients whose liver is already significantly damaged may have a greater risk of complications.

If you develop severe abdominal pain, persistent vomiting, high fever, significant bleeding or other concerning symptoms after treatment, contact your healthcare team promptly.

Do not assume that every symptom after SIRT is normal. Your treating team should determine whether a symptom represents an expected treatment effect or requires further assessment.

12. SIRT and Other Options for Treating Liver Cancer

There are several approaches to treating liver cancer. The most appropriate treatment depends on the cancer type, tumour stage, liver function and overall health.

SIRT does not replace all other liver cancer treatment options.

In some cases, it may be used alone. In other situations, it may be combined with or followed by another treatment.

The treatment plan should be determined by a specialist team after reviewing the patient’s individual medical information.

13. SIRT and Liver Transplantation

One question that concerns some liver cancer patients is whether SIRT can be used when liver transplantation is being considered.

In selected situations, liver-directed treatments may form part of an overall treatment strategy before transplantation. The role of SIRT depends on factors such as the type and extent of cancer, liver function, tumour characteristics and transplant eligibility.

When liver transplantation is being considered, cancer treatment decisions should be coordinated with the transplant team.

Patients searching for the best liver transplant surgeon in India should consider a transplant centre capable of providing comprehensive evaluation and multidisciplinary care rather than focusing only on a single procedure.

A transplant assessment may involve imaging, blood tests, tumour evaluation, liver-function assessment and consultations with several specialists.

SIRT does not guarantee eligibility for liver transplantation. Transplant eligibility must be determined by the transplant team according to the patient’s individual clinical circumstances and applicable transplant criteria.

14. Recovery and Follow-Up After SIRT

Recovery after SIRT varies between patients.

It is common for some patients to experience fatigue for several days or weeks following treatment. Your doctor may recommend limiting strenuous activity initially and gradually returning to normal activities.

Follow-up is an important part of the treatment process.

Your healthcare team may arrange:

• Blood tests
• Liver-function tests
• CT or MRI scans
• Tumour-marker tests when appropriate
• Clinical examinations
• Regular specialist consultations

Follow-up imaging may be performed several weeks after treatment to evaluate how the tumour has responded.

It is important to remember that the appearance of liver tumours can change after treatment. A follow-up scan may not always provide an immediate or simple answer about treatment success.

Doctors therefore consider the complete clinical picture, including symptoms, blood tests, imaging findings and the patient’s overall condition.

Conclusion

Selective Internal Radiation Therapy (SIRT) is a specialised treatment that uses tiny radioactive microspheres to deliver radiation directly to selected liver tumours.

By using the tumour’s blood supply as a pathway, SIRT aims to provide a concentrated radiation treatment while limiting exposure to surrounding healthy tissue.

SIRT may be considered for selected patients with primary or metastatic liver tumours when surgical removal is not appropriate. However, it is not suitable for everyone and does not always result in complete tumour remission.

Patients and their families should discuss treatment options with a specialised liver cancer, hepatobiliary or liver-transplantation team. A detailed evaluation can help determine whether SIRT, surgery, transplantation, ablation, systemic treatment, or a combination of approaches is appropriate.

Frequently Asked Questions

1. What is SIRT used for?

SIRT is used to treat selected liver tumours, including certain primary liver cancers and cancers that have spread to the liver. It is particularly considered when surgical removal is not appropriate.

2. Is SIRT painful?

Local anaesthetic is generally used where the catheter is inserted. Some patients may experience discomfort, abdominal pain or a warm sensation during the procedure, particularly when contrast material is injected.

3. How long does SIRT treatment take?

The actual SIRT procedure generally takes approximately one to two hours, although the overall treatment process also includes pre-treatment assessment and planning.

4. Can SIRT cure liver cancer?

SIRT can provide effective local control for selected liver tumours, but it does not always cure liver cancer. Treatment goals vary depending on the cancer type, tumour extent, liver function and the patient’s overall condition.

5. Can SIRT be performed before a liver transplant?

In selected cases, liver-directed treatments such as SIRT may form part of an overall treatment plan while transplantation is being considered. However, SIRT does not automatically make a patient eligible for liver transplantation. The transplant team must assess the patient’s cancer, liver function and other eligibility criteria.

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