Stereotactic Body Radiotherapy (SBRT)

Overview

If you have specific types of cancer, such as lung cancer or pancreatic cancer, your doctor may advise you to undergo stereotactic body radiotherapy (SBRT). It's a very exact procedure that allows your doctor to precisely target your malignancies.

SBRT (stereotactic body radiotherapy) is a form of radiation treatment. This method is sometimes referred to as stereotactic ablative radiotherapy (SAR) when it is performed on the body rather than the brain.

To treat cancers and other diseases across the body, the treatment employs a large number of carefully targeted radiation beams. SBRT is used to treat cancers that have spread to the lungs, spine, liver, neck, lymph nodes, or other soft tissues.

SBRT is not a standard sort of surgery because there is no incision. SBRT, on the other hand, employs 3D imaging to precisely deliver high doses of radiation to the afflicted region. This suggests that there is very little harm to the healthy tissue around it. Stereotactic radiosurgery, like other kinds of radiation, operates by destroying the DNA of the targeted cells. The damaged cells are thus unable to proliferate, causing tumors to shrink.

What is Stereotactic Body Radiotherapy (SBRT)?

Stereotactic Body Radiation Therapy (SBRT) is a therapy process that is similar to central nervous system (CNS) stereotactic radiosurgery, except that it treats cancers that are not in the CNS.

 A stereotactic radiation treatment for the body entails the use of a specifically constructed coordinate-system to precisely localize malignancies in the body in order to treat them with restricted but extremely accurate treatment fields. 

SBRT entails either a single high-dose radiation therapy or a series of fractionated radiation treatments (usually up to 5 treatments). A high powerful biological dosage of radiation is supplied to the tumor, enhancing cure rates in a way that normal conventional radiation treatment could not.

Similarly, because this specialized kind of radiation involves the utilization of numerous radiation beam angles, skilled Radiation Oncologists trained in this approach may safely deliver high doses of radiation with a very steep dose gradient outside the tumor and into the surrounding normal tissue.

This method is now being employed in cases where therapeutic choices were previously restricted. It is presently most typically utilized to administer an ablative dose of radiation to individuals who have a restricted number of recurrent sites. Limited disease in recurrent lymph nodes, the lungs, the spine, and the liver are examples.

How SBRT Differs from Conventional Therapy?

Radiation is provided in relatively tiny doses over many weeks in conventional therapy, with patients getting daily treatments during that period. SBRT allows physicians to give a higher cumulative dosage of radiation over the course of significantly fewer sessions. SBRT offers much better results than traditional radiation treatment.

Whereas traditional therapy has a two-year success rate of 30 to 40%, SBRT has a success rate of 80 to 90% – equivalent to resection surgery but with significantly less hazards. Despite the fact that SBRT uses a larger biological dose of radiation, patients have reported less side effects, such as pneumonia. SBRT's most prevalent adverse effect is mild tiredness for one week after treatment.

What’s the Difference between IMRT& SBRT?

IMRT, or intensity-modulated radiation therapy, is a method of administering external radiation that aids in the shaping of the radiation beam. It is often used for patients undergoing conventional radiation. This therapy makes use of technology to shape the radiation beam so that it fits tightly around normal body components. IMRT is commonly used by doctors to treat head and neck cancer. SBRT patients may also undergo IMRT. What works best for you will be determined by your healthcare practitioner.

They may also use other ways to deliver external radiation, like:

1. Three-dimensional conformal radiation therapy (3D-CRT): When planning radiation therapy, healthcare practitioners employ computed tomography (CT) scans to build 3-dimensional (3D) pictures of the tumor. With these 3D scans, healthcare practitioners will be able to determine how to treat the cancer while conserving healthy tissue. 3D planning is used in all current radiation treatments, including IMRT and SBRT.
2. Image-guided radiation therapy (IGRT): Healthcare practitioners capture photographs of the region being treated on a daily basis and compare them to photos taken before therapy began. They can make modifications based on these photos to ensure that the therapy is given accurately.

Types of Stereotactic Body Radiotherapy (SBRT)

Doctors use two types of technology to deliver radiation during SBRT:

• A medical linear accelerator (LINAC):

It customizes high-energy x-rays or electrons to conform to the shape of a tumor and destroy cancer cells while sparing normal tissue in the surrounding area. It has numerous built-in safety measures to guarantee that it delivers the correct dose and is frequently examined by a medical physicist to confirm that it is operating properly.

LINAC machines are also known by their manufacturer's brand names, such as CyberKnife and TrueBeam. For bigger tumors, these devices may conduct SRS in a single session or across two to five sessions (fractionated stereotactic radiotherapy).

The linear accelerator employs microwave technology (similar to radar) to accelerate electrons in a section of the accelerator known as the "wave path," which then collides with a heavy metal target to create high-energy x-rays. As they depart the machine, these high intensity x-rays are molded to correspond to the shape of the patient's tumor, and the personalized beam is directed at the patient's tumor. 

A multileaf collimator included inside the machine's head is typically used to shape the beam. The patient is positioned on a movable treatment couch, and lasers are utilized to ensure that the patient is in the correct posture.

The treatment couch may be moved in a variety of directions, including up and down, right and left, in and out. The beam emerges through a section of the accelerator known as a gantry, which may be spun around the patient. By rotating the gantry and repositioning the treatment couch, radiation may be given to the tumor from a variety of angles.

• Proton beam (charged particle): 

It is the most recent kind of stereotactic radiation and is only offered in a few research institutes in the United States, while the number of centers delivering proton beam treatment has expanded dramatically in recent years. It can treat body cancers with fractionated stereotactic radiation over numerous sessions. Proton beam SBRT may be utilized to treat cancers in areas of the body that have already undergone radiation treatment or that are close to vital organs. 

There is less radiation dosage outside of the tumor with proton treatment. In conventional radiation treatment, x-rays continue to deliver radiation doses even after they have left the patient's body. This implies that radiation causes harm to neighboring healthy tissues, perhaps resulting in adverse effects.

When You Might Have Stereotactic Radiotherapy?

SBRT involves the delivery of numerous high-dose radiation beams at various angles with the goal of entirely eliminating the targeted tumor. People with well-defined, tiny tumors who are unable to undergo traditional surgery are the greatest candidates for SBRT.

SBRT is most commonly used to treat tiny primary (original) tumors, but it is also being investigated for persons with oligometastases (a small number of metastatic tumors).

1. Primary Tumor:

SBRT is primarily used to treat early-stage lung tumors that are inoperable. Your tumor may be considered inoperable owing to its location or if you have specific health problems, such as advanced age, that make lung cancer surgery problematic.

SBRT can occasionally be used instead of surgery for persons with inoperable stage 1 lung cancer, and it has the same effectiveness and long-term survival rates as standard surgery.

Tumors must be tiny, generally less than 5 centimeters (2 to 3 inches) in diameter, and cannot be located too close to the lungs, heart, or other important structures for SBRT to be successful.

SBRT substantially doubles survival in adults with stage 1 lung cancer when compared to traditional radiation therapy, according to a 2019 research published in Lancet Oncology.

2. Oligometastases:

Oligometastases are classified as localized cancer spread for whom local ablative treatment may be curative.

If you have one or a few tiny metastatic tumors in your lungs, your oncologist may recommend SBRT (but generally no more than five). These metastases might be caused by a primary tumor in the lung or a primary tumor in another section of the body.

SBRT may also be used to treat oligometastases that have spread from the lungs (most often in the liver, brain, and adrenal glands) or from other primary tumors in the body.

What Happens Before SBRT?

Before SBRT can begin, you will have a battery of imaging tests to find the tumor and map the exact region to be treated. A magnetic resonance imaging (MRI) or computed tomography (CT) scan, as well as four-dimensional imaging, which records the target area as it moves during inhalations and exhalations, may be used. This is normally done over the course of one or more sessions prior to the scheduled surgery.

A model of your upper body will also be created, and you will lie on it on the day of your treatment to remain motionless and in position during the operation. You are positioned optimally on a huge plastic bag filled with a quick-setting, plaster-like substance to produce the mold.

Permanent tattoo markings roughly the size of a pin will also be put on your skin to guarantee that the SBRT beams are focused appropriately in three dimensions. If desired, they can be eliminated later using laser skin treatments.

Once the coordinates are mapped and the radiation dose is calculated, SBRT can proceed as scheduled. In some cases, SBRT and the set-up for it can be done on the same day (typically if only a single session is required). Other times, set-ups are scheduled a week or two in advance.

• Timing of the preocedure:

Each SBRT session might last anywhere from 20 to 60 minutes, depending on the location and size of the targeted tumor. Some people may just need one session, while others may need up to eight sessions spread out over several days. 

You can plan to spend at least two to three hours in the facility due to set-up and pre-treatment exams. If the treatment center has a full schedule, it may take longer.

• Location of the procedure:

SBRT is performed in a dedicated room with a linear accelerator at a hospital's radiology unit or a specialist radiology clinic.

The apparatus consists of a moveable flatbed on which you lie down and a big rotating gantry that can be moved around your body to deliver radiation from various angles. Some later variants come with a robotic arm.

• What to Wear

You may be asked to change into a hospital gown, so wear loose-fitting clothes that are easy to take off and put on. Please leave any jewelry at home.

Shoes, socks, and underwear can be worn throughout the operation, but bras must be removed.

If you have any implanted medical devices, such as a pacemaker, artificial heart valve, stent, aneurysm clip, cochlear implant, or neurostimulator, notify your healthcare practitioner ahead of time.

• Food and Drink

On the day of the operation, you will usually be requested to refrain from eating, drinking, or taking anything by mouth after midnight.

Inform your practitioner if you use any drugs on a regular basis. You may be able to take them with a sip of water in some circumstances. Others may need you to wait till after the surgery to take them.

• Cost and Insurance

The cost of SBRT varies depending on your region and the institution used, with the typical cost in 2016 being at $27,145. While this is around half the cost of wedge resection surgery, it is still a costly treatment that requires prior clearance from your health insurer.

Check your coverage for the copay/coinsurance charges before and after your deductible is met to estimate your out-of-pocket payments for the treatment. The majority of insurance plans will cover a fraction of the expense. If you have already reached your yearly out-of-pocket maximum, your whole operation may be covered.

Always check to see if the radiology unit and its employees are in-network providers. If they aren't, inquire with your oncologist about in-network providers. Out-of-network providers will almost always be more expensive.

• What to Bring:

Aside from your driver's license (or other official forms of ID), insurance card, and an accepted mode of payment, you normally don't need to bring anything to an SBRT session.

If you wear contact lenses on the day of the treatment, you will be required to remove them, therefore bring glasses and a lens case/solution with you. Similarly, dentures must be removed, so bring a case if you wear them.

If you feel chilly easily, you can bring a blanket and slippers to cover your legs and feet, however most radiology units have blankets and slippers available if you ask.

What Happens During SBRT?

Stereotactic body radiation treatment is painless and similar to obtaining an X-ray. During treatment, your healthcare professional will want you to be as comfortable as possible. It's vital to remember that you can interrupt the therapy session if you feel worried or disturbed. The following stages may occur during your treatment:

You may need to undress depending on the region being treated, so wear clothing that are simple to take off and put on.

You will be lying down on the same treatment table that you used for simulation.

Because therapy sessions might range anywhere from 15 minutes to more than an hour, your healthcare practitioner will make sure you're comfortable when they position you for treatment.

Technicians working under the supervision of your healthcare professional operate the radiation equipment from a protected chamber, avoiding exposure to radiation. They can see you on a television and hear you on an intercom.

The linear accelerator, which provides the radiation beam (or beams), will not come into contact with you. The radiation will be delivered via a large arm that will be draped over you as you lie on the treatment table.

During treatment, you will be required to remain motionless.

The machine arm may be moved around the table by your healthcare professional. This is done to alter the angle of the radiation beam.

You won't feel anything, although the machine may make some noise as it travels.

Risks & Possible Complications

Stereotactic radiosurgery doesn't involve surgical incisions, so it's generally less risky than traditional surgery. In traditional surgery, you may have risks of complications with anesthesia, bleeding and infection.

Early complications or side effects are usually temporary. They may include:

1. Fatigue: Tiredness and fatigue may occur for the first few days after SBRT.
2. Swelling: Swelling at or near the treatment site can cause signs and symptoms such as a temporary increase in pain. Your doctor may prescribe anti-inflammatory medications (corticosteroid medications) to prevent such problems or to treat symptoms if they appear.
3. Nausea or vomiting: Some patients may experience temporary nausea or vomiting if the radiated tumor is near the bowel or liver.

Rarely, people may experience late side effects, months after treatment, although this varies for each body site. Your physician will discuss potential risks more thoroughly with you. These may include:

1. Weakened bones that may break
2. Changes affecting the bowel
3. Changes in the lungs
4. Changes in the spinal cord
5. Developing a new cancer (secondary cancer)
6. Swollen arms and legs (lymphedema)

Conclusion

Stereotactic body radiation therapy (SBRT) is a technical innovation in the field of radiation therapy. It varies from conventional radiation treatment in that it provides extremely concentrated radiation over a short period of time (days, not weeks). SBRT is used to treat tiny tumors that have not progressed to other organs. It delivers high doses of radiation while reducing the quantity of radiation reaching neighboring healthy tissue and organs, which might cause injury.

Stereotactic radiosurgery and radiation all function in the same way. The specialized equipment directs radiation beams onto a tumor or other target. Each beam has minimal effect on the tissue it passes through, but a concentrated dosage of radiation is given to the point where all the beams connect.

The high dosage of radiation supplied to the afflicted region shrinks tumors and causes blood vessels to seal down over time after treatment, depriving the tumor of its blood supply.

Stereotactic body radiation therapy is used to treat several kinds of cancer, including:

• Lung cancer.
• Prostate cancer.
• Liver cancer.
• Pancreas cancer.