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Selective Internal Radiation Therapy (SIRT)
External Radiation therapy for the liver has generally been limited in multifocal disease because the high radiation doses delivered to normal liver tissue can lead to liver failure. Selective internal radiation therapy takes advantage of the general principle that tumor metastases in the liver generally have an increased blood supply. A new FDA approved therapy involving radioactive microspheres (yttrium-90) can be used to safely irradiate colon cancer liver metastases. Know by the trade name SIR-Spheres®, these microspheres are delivered into the arterial circulation of the liver. They will congregate in highest concentration within areas of increased blood flow around the cancer deposits. Lethal doses of radiation can be delivered to the tumor while sparing more normal areas of liver. Thus wide spread liver disease can be treated without causing liver failure.
Do I qualify for this therapy? Most patients are candidates for this therapy. Three things will determine which patients are appropriate candidates. First, liver function has to be normal. Generally this means that the total bilirubin is less than 2 and that there are no other signs of liver damage. Second, disease should be multifocal and not amenable to surgical resection or RF-ablation. The best responses occur with complete removal of the tumor if possible. Some patients may have disease that could be resected or treated with RF-ablation, but for other medical reasons cannot have these procedures done. These patients would also be considered for Selective Internal Radiation Therapy. Third, the arterial supply to the liver has to be appropriate and we have to document that the treatment particles will not pass through the liver to the lungs. These factors can only be known after completion of a pre-treatment simulation. This is performed as a last step prior to scheduling the actual embolization using the yttrium-90 labeled microspheres into the liver.
I want to be evaluated what do I do? Schedule an appointment to discuss your case. We will answer your questions and describe the complete process. If it looks like you will be a good candidate and you want to proceed we will schedule an outpatient angiogram and go on from there. Out-of-town patients will be evaluated in a single day and can submit copies of imaging and lab reports prior to visiting.
Pre procedure evaluation. This occurs as an outpatient and takes generally a full day. We begin with a review of your imaging studies (CT, MRI, ultrasound, PET) and medical history with lab work. Then you will undergo a planning arteriogram to evaluate the blood supply to your liver. You will also undergo CT liver imaging with hepatic arterial injection of contrast. Liver/lung shunt evaluation will be performed with injection of Technetium 99m labeled MAA into the hepatic artery. This in essence simulates the actual deliver of the yttrium-90 nmicrospheres and allows me to evaluate the expected distribution of the microspheres within the liver and to make sure that too many spheres don't end up outside of the liver in the gut or within the lungs. If the hepatic arterial anatomy is appropriate and there is no evidence of significant shunt of spheres to the lungs or intestine then we will schedule a date for the actual implantation of the ytttium labeled microspheres.
Yttrium 90 microsphere treatement of the liver: Once it has been determined that you are an appropriate candidate for the therapy a dose will be ordered from Sirtex Medical. This will take 1-2 weeks to arrive and you will be scheduled to come in the morning the dose arrives. You will receive intravenous fluids and premedications to help control nausea/pain and to limit acid production in the stomach. You will undergo a second angiogram (very much similar to the planning angiogram) during which the spheres will be instilled into half of your liver. Once the treatment is complete the catheters will be removed and you will be observed in the hospital. More imaging will be performed to confirm that the dose went to the liver and the liver only. If you do well, you will be discharged before 24 hours have passed such that this will be considered an outptatient procedure. If you have any complications like fever, vomiting or pain then you will stay in the hospital until these have resolved. Most patients tolerate the procedure quite well and are discharged as outpatients. Post procedure handout. Only half of the liver is treated at a time to limit toxicities and complications. Follow-up will occur 1-2 weeks post procedure and then you will return to treat the other half of your liver 4 weeks aftter the initial treatment. Total time to treat the whole liver therefore takes one month.
FDA Approval Summary: Safety and Effectiveness of SIR Spheres
Alternative Liver treatments. Other therapies such as RF-ablation and chemoembolization (TACE) are also performed to treat metastatic disease to the liver. |
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