Stereotactic Radiosurgery

• Researchers are exploring the use of stereotactic radiosurgery (SRS) to treat breast cancer, prostate cancer, and other disorders⁽¹⁾. SRS commonly treats tiny brain tumors and brain disorders using focused radiation beams.
  Meanwhile, stereotactic body radiotherapy (SBRT) treats body malignancies with high-precision radiation⁽²⁾.
• One-third of patients treated with SRT and SRS experience immediate side effects (ISE), which are typically mild to moderate⁽³⁾. Dizziness or vertigo, unrelated to increased brainstem dosages, are common among individuals with acoustic neuromas (benign brain tumors).
• A stereotactic radiosurgery literature review from the World Journal of Radiology includes articles from 1993 to 2013, 20 case series, and clinical trials⁽⁴⁾. The review indicates that SRS is safe and effective for various gynecological conditions, including ovarian, endometrial, and cervical cancer.
• Radiosurgery is generally safe and does not cause significant complications⁽⁵⁾. Complications such as infections or pin-site bleeding are usually rare, and swelling around a tumor can occur after the procedure. 

What Is Stereotactic Radiosurgery?

Stereotactic radiosurgery (SRS) uses focused beams of radiation to treat various types of tumors, such as those in the brain, lungs, and liver⁽⁶⁾.

The procedure uses 3D imaging to target high radiation levels directly in the affected area⁽⁷⁾. Unlike conventional radiation therapy, the method avoids damaging the surrounding tissue and makes no incision.

SRS treats small brain tumors and functional brain problems. Stereotactic body radiotherapy (SBRT) uses the same high-precision radiation as cranial SRS to treat body cancers⁽⁸⁾.

Radiation oncologists, neurologists, medical radiation physicists, dosimetrists, radiation therapists, and radiation therapy nurses are part of the treatment team members⁽⁹⁾.

Notably, patients with primary brain tumors and brain metastases should be treated by a multidisciplinary team that is among the most skilled in the world⁽¹⁰⁾. The team may include radiation oncologists, medical physicists, neurologists, neuroradiologists, and expert nursing staff. 

Types of Stereotactic Radiosurgery

There are various types of systems that can deliver stereotactic radiosurgery. The most commonly used are the Gamma Knife and Linear Accelerator (LINAC) based systems⁽¹¹⁾.

Gamma Knife surgery is a computer-guided, painless procedure where the delivery of radiation is highly concentrated on brain tumors and lesions⁽¹²⁾. 

Also, suppose individuals cannot undertake surgery due to condition and age. In that case, they may undergo conventional surgery to prevent tumor regrowth.

Unlike other forms of SRS, Gamma Knife radiosurgery does not involve an incision⁽¹³⁾.

Instead, Gamma Knife radiosurgery focuses around 200 microbeams of radiation with submillimeter precision on a tumor or other target. Although each proton beam has a little impact on the brain tissue it traverses, a high dosage of radiation is given at the intersection of all beams.

On the other hand, a medical linear accelerator (LINAC) modifies high-energy X-rays or electrons to fit the shape of a tumor and kill cancer cells while sparing normal tissue⁽¹⁴⁾.

 This equipment comes with several fail-safe safeguards already installed to guarantee that it dispenses the appropriate quantity. A medical physicist performs routine maintenance checks on the LINAC to verify that it continues to function appropriately.

Although each modality has many advantages and disadvantages, they all share the same goal of delivering photons to a target⁽¹⁵⁾. They all use a generator or radiation source to deliver the radiation and use head frames. Also, the use of computerized algorithms to precisely provide the radiation.

Uses of Stereotactic Radiosurgery

Stereotactic radiosurgery is a precise form of therapeutic radiation that can treat cancer, epilepsy, trigeminal neuralgia, and arteriovenous malformations⁽¹⁶⁾.

Meanwhile, the literature review of stereotactic radiosurgery used the PubMed search engine⁽¹⁷⁾. The study included 20 case series and clinical trials from 1993 to 2013.  

The safety and efficacy of this procedure have been demonstrated in various gynecological diseases, such as ovarian, endometrial, and cervical cancer treatment⁽¹⁸⁾.

SRS is a potential second-line treatment for individuals with recurrent primary conditions who cannot endure surgery or radiation therapy⁽¹⁹⁾.

Still, further study is necessary to identify a high dose of radiation and fractionation patterns, patient groups, and long-term morbidity and survival.

The Difference Between Stereotactic Radiation Therapy and Standard Radiation Therapy

SRS treatment is a non-surgical approach that provides more radiation in fewer sessions than standard radiation therapy⁽²⁰⁾. 

This therapy is only feasible because of improved radiation technologies that give maximal dosage to the target while minimizing exposure to healthy tissue. The objective is to eliminate the tumor while simultaneously achieving long-term, secure local control.

The Benefits and Risks of SRS Treatment 

SRS helps avoid surgical risks of bleeding, infection, and anesthesia. The treatment may be performed as an outpatient procedure. Only a slight interruption of other therapies, such as chemotherapy, is required⁽²¹⁾. 

The results of brain metastases treated with SRS seem to be equivalent to those treated with surgical excision of the tumor.

In addition, stereotactic radiosurgery combines 3D target localization with several cross-fired beams from a high-energy radiation source to accurately irradiate abnormalities in typically cancerous lesions⁽²²⁾.

It is feasible to deliver large doses to the target while simultaneously reducing the amount of radiation exposure to the surrounding region’s normal tissue. Ideal destruction implies no normal tissue damage⁽²³⁾.

In conventional radiotherapy, spatial precision is secondary since normal tissues are safeguarded by providing the radiation dosage over many weeks in several treatment sessions⁽²⁴⁾.

Radiosurgery demands accuracy. Stereotactic radiosurgery protects normal tissue by targeting the abnormal lesion and employing cross-firing to limit exposure of the normal tissues⁽²⁵⁾.

Patients should note the potential risk for anesthesia-related issues, bleeding, and infection during standard surgery⁽²⁶⁾. 

Early complications are usually temporary. Still, patients who have had stereotactic radiosurgery may have feelings of fatigue for the first weeks after the treatment.

Symptoms such as headache, nausea, and vomiting result from brain swelling at or around the treatment site. A physician can give anti-inflammatory drugs like corticosteroid medications to prevent or treat symptoms of such conditions.

A region of the scalp that is in touch with a device connected to the head can become irritated, red, or itchy during the treatment. Some people experience a transient reduction in the quantity of hair they have.

The therapy makes it possible to provide high doses to the target while limiting exposure to the normal tissue in the surrounding area. Ideal destruction entails no normal tissue damage⁽²⁷⁾.

 A team with extensive expertise in SRS application must perform the treatment to minimize the risk, considering that the target is the brainstem and the radiation dosage is significant⁽²⁸⁾.

Side Effects 

Despite the rising use of fractionated stereotactic radiation therapy and stereotactic radiosurgery, the occurrence and type of immediate side effects (ISE) associated with these treatment modalities are poorly understood⁽²⁹⁾. 

One-third of patients treated with SRT and SRS experienced typically mild to moderate complexities. Patients with acoustic neuromas often feel dizzy, a possible side effect unrelated to increased brainstem dosages⁽³⁰⁾. 

The studies cannot identify a correlation between ISE and larger margin or maximum radiation therapy dosages⁽³¹⁾. Additionally, no definitive conclusion can be formed regarding the influence of corticosteroids administered before SRS/SRT on the incidence of ISE.

Meanwhile, researchers at Johns Hopkins Medicine have found a few possible adverse responses to the SRS. These reactions include the following:

• Fatigue
• Headache
• Skin irritation in the affected and treated area
• Gastrointestinal symptoms, like diarrhea, nausea, or vomiting 
• Hair loss in the treated area
• Neurological symptoms, such as weakness, seizure, numbness, or tingling

Complications

A preliminary analysis of our experience at the University of Texas M.D. Anderson Cancer Center revealed that complications were more common when treating lesions in regions of the brain associated with eloquence than in other brain regions⁽³²⁾. 

Meanwhile, radiosurgery is generally safe and does not cause significant complications. Issues such as infections or pin-site bleeding are usually rare, and swelling around a tumor can occur after the procedure is completed⁽³³⁾. 

In rare cases, a seizure can occur⁽³⁴⁾. The patient’s family members and caregivers should contact 911 and alert the patient’s doctor to reduce the likelihood of the patient having seizures. Seizures may be avoided by taking the appropriate anticonvulsant medicine as directed.

One of the most common late complications after radiation therapy is radiation necrosis, in which the body does not clear the tumor cells adequately⁽³⁵⁾. In some cases, this can lead to further brain swelling and require an increased dose of Decadron. 

In refractory cases, necrosis can also be treated by performing surgery to remove dead tissue or administering hyperbaric oxygen. Having a close follow-up with a radiation oncologist or neurosurgeon is also essential⁽³⁶⁾.

A tumor growing in another part of the brain is possible, as the treatment is focused on a specific area⁽³⁷⁾. This occurrence can lead to the treatment being repeated in the new treatment area of tumor growth. Generally, it is necessary to limit the number of tumors treated in a single session to four.

In addition, a radiation oncologist and a neurosurgeon can extend the duration of the treatment for a patient with a particular type of tumor⁽³⁸⁾. However, they will consider the patient’s age, the type of tumor, and any previous treatments they have had.

Qualifications: Good Candidates for SRS

This radiation therapy is most effective with very small, well-defined, and detectable tumors (like CT or MRI)⁽³⁹⁾. If a tumor is near or touches another organ, it may not be safe to undergo such a procedure. The effectiveness of stereotactic radiation therapy relies on the tumor’s size, shape, location, and cancer type.

Also, patients whose illness is not physically accessible or is too advanced for neurosurgery and those who cannot endure anesthesia are candidates for stereotactic radiosurgery⁽⁴⁰⁾.

Individuals who want to try SRS should look for team experts who are pioneers in the delivery of stereotactic radiosurgery, directing clinical studies that have prolonged patients’ lives.

Preparation

In stereotactic radiosurgery, radiation oncology and neurosurgery professionals work as a team⁽⁴¹⁾.

A specialist in dosimetry specifies how the beams should be directed, and a physicist estimates the quantity of radiation the individuals should get, balancing risk and possible efficacy. Maximizing the therapy to abnormal tissues while conserving good tissues around the abnormal location is a crucial aspect of process design.

These medical specialists devote around two weeks to set up the procedure. In the case of an emergency, the amount of time spent preparing may be shortened.

Preparation for stereotactic radiosurgery and stereotactic body radiation vary depending on the condition and location of the body to be treated. Individuals should do the following steps⁽⁴²⁾:

1. Eat after midnight or the night before the operation.
2. Discuss with their physician whether to take the regular prescriptions the night before or the morning of the treatment.
3. Wear loose-fitting, comfortable clothing. The following should not be worn during SRS of the brain or spine:

• Jewelry
• Nail polish
• False teeth 
• Wigs and hairpieces
• Eyeglasses
• Contact lenses
• Cosmetics 

Meanwhile, when the individuals first see radiotherapy equipment, they may experience anxiety⁽⁴³⁾. The therapy machine spins around the individuals, although it does not affect them in any way.

The radiographers will describe what individuals see and hear before the first treatment⁽⁴⁴⁾. In certain sections, the treatment rooms have docking stations for music players so patients can listen to their favorite songs.

An outpatient clinic can be used for treatment⁽⁴⁵⁾. After the operation, preparation, treatment, and monitoring might take several hours in the outpatient clinic. Additionally, patients need a ride home from a friend or family member.

Treatment or Procedure

Individuals must remain motionless for the duration of the therapy, which lasts 30 to 60 minutes. There is no cutting or incision involved⁽⁴⁶⁾. 

The radiographers attach the mask or head frame to the treatment table⁽⁴⁷⁾. The staff then leave the room before the treatment begins to reduce their likelihood of exposure to the radiation.

A head holder will be put on the head of an individual who will undergo treatment for a brain lesion⁽⁴⁸⁾. Then, they will lie on a hard surface, similar to what they can find in an MRI or CT scan.

The treatment team will program the machine and deliver the X-rays for the patient’s treatment, which includes several doses of focused X-rays⁽⁴⁹⁾. 

The radiographers can see and listen to the patients through the CCTV in the next room. Physicians can notify them if there is a need to move to a different location.

The device produces whirring and beeping noises⁽⁵⁰⁾. However, the patients cannot feel the radiation when it is administered.

Once the procedure is over, the radiographers will assist the patients away from the machine. After removing the mask or frame, patients can return to their hospital rooms or go home.

After Surgery 

A recovery area will be provided after the procedure, where patients will be monitored to ensure everything went well⁽⁵¹⁾. 

Individuals may have certain adverse effects during or after SBRT⁽⁵²⁾. The nature and intensity of adverse effects vary on several factors, including:

• Radiation dosage
• Tumor location
• Number of treatments (fractions)

The body only absorbs about a small amount of radiation. Stereotactic body radiotherapy has fewer side effects than standard therapy⁽⁵³⁾. These side effects can be temporary, which include:

• Inflammation of the treatment region
• Fatigue
• Nausea and vomiting if the treatment location is near the abdomen or liver 

There may also be adverse effects that occur weeks or months after the completion of SBRT⁽⁵⁴⁾. Examples include:

• Changes to the skin and hair that may occur four to six weeks after the procedure
• Coughing and rib discomfort that may occur months after SBRT therapy if the lungs are affected
• Losing part or all of the hair in the treated region
• Seeing pink or tanned skin surrounding the treatment region 

Expected Results

Depending on the condition being treated, stereotactic radiosurgery has a progressive therapeutic effect on the following⁽⁵⁵⁾:

1.Trigeminal neuralgia

Trigeminal neuralgia is treated using stereotactic radiosurgery, which concentrates radiation on the trigeminal nerve. SRS damages the nerve enough to inhibit pain signals from reaching the brain⁽⁵⁶⁾. 

This technique has a success rate of over 70%, with few adverse effects⁽⁵⁷⁾. Still, up to 50% of individuals with treatable pain may have a recurrence.

SRS produces a lesion that inhibits pain signal transmission along the trigeminal nerve⁽⁵⁸⁾. Many individuals experience pain relief within a few weeks, while others may take many months.

2. Benign tumors (including vestibular schwannoma)

SRS successfully treats vestibular schwannoma, tiny tumors that arise from the vestibular nerve (or acoustic neuroma)⁽⁵⁹⁾.

After stereotactic radiosurgery, the tumor may diminish over the course of 18 to 24 months. The primary objective of therapy for benign tumors is to prevent future tumor formation⁽⁶⁰⁾.

3. Malignant tumors

On average, malignant (cancerous) tumors may diminish within a few months⁽⁶¹⁾.

One study reviewed and evaluated the role of stereotactic radiosurgery or stereotactic radiotherapy (SRS/SRT) for malignant skull base tumors⁽⁶²⁾. Skull base tumors continue to be difficult to cure. Often, their entire resection is challenging.

SRS/SRT is an effective therapeutic option for remaining or recurring cancers following surgical extirpation (destruction) in instances of primary malignancies of the skull base⁽⁶³⁾. If skull base metastases and skull base invasion are reasonably confined, they may qualify for SRS/SRT.

4. Arteriovenous Malformations (AVMs)

AVMs, or arteriovenous malformations, are abnormal tangles of arteries and veins that may develop in the brain⁽⁶⁴⁾. When individuals have an AVM, blood will skip the smaller blood vessels and travel straight from their arteries to their veins (capillaries). 

The natural flow of blood through the body may be disrupted by AVMs, which can eventually lead to either bleeding (hemorrhage) or a stroke.

The AVM may be removed via stereotactic radiosurgery, leading to the damaged blood arteries being sealed up in the long run.

Radiation treatment causes aberrant blood vessels of AVMs in the brain to thicken and shut. This procedure might take at least two years⁽⁶⁵⁾.

Long-Term Outlook

Following local recurrence after stereotactic radiosurgery (SRS), the optimal treatment plan remains uncertain⁽⁶⁶⁾. While SRS has been widely examined before retreatment, few studies have focused on retreatment results. 

Presented here are the results of the second round of SRS treatment for the local recurrence of brain metastases treated with SRS in the past₍₆₇₎.

Repeating LINAC-based SRS after recurrence remains a viable treatment option in a subset of individuals, resulting in long-term survival and local control. Radionecrosis in high-risk persons exceeds 20% and mimics historical levels⁽⁶⁸⁾.

Recovery

In the following stereotactic radiosurgery, bandages are placed over the pin sites of the stereotactic frame. These bandages should be removed the next day⁽⁶⁹⁾.

 Individuals may stay in the hospital overnight for monitoring⁽⁷⁰⁾.

Individuals may also note that following the treatment, they will be given the proper medications if they have headaches, nausea, or vomiting⁽⁷¹⁾. However, after the surgical procedure is complete, patients can resume their regular diets, including the consumption of food and beverages.

Some individuals report mild sensitivity at the puncture sites. Occasionally, swelling may also occur around the pin sites. If the swelling does not make one uncomfortable, patients may resume normal activities the next day.

It is also crucial for patients to talk to their attending physicians regularly. So they will know specific instructions on appropriate follow-up exams to monitor their progress. 

---

1. Stereotactic radiosurgery
   https://www.mayoclinic.org/tests-procedures/stereotactic-radiosurgery/about/pac-20384526
2. Stereotactic Radiosurgery (SRS) and Stereotactic Body Radiotherapy (SBRT)
   https://www.radiologyinfo.org/en/info/stereotactic#
3. Immediate side effects of stereotactic radiotherapy and radiosurgery
   https://pubmed.ncbi.nlm.nih.gov/10030253/
4. Use of stereotactic radiosurgery in the treatment of gynecologic malignancies: A review
   https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4072821/
5. Stereotactic Radiosurgery
   https://www.aans.org/en/Patients/Neurosurgical-Conditions-and-Treatments/Stereotactic-Radiosurgery
6. Stereotactic radiosurgery
   https://www.mayoclinic.org/tests-procedures/stereotactic-radiosurgery/about/pac-20384526
7. Ibid.
8. Stereotactic Radiosurgery (SRS) and Stereotactic Body Radiotherapy (SBRT)
   https://www.radiologyinfo.org/en/info/stereotactic
9. Stereotactic Radiosurgery
   https://www.aans.org/en/Patients/Neurosurgical-Conditions-and-Treatments/Stereotactic-Radiosurgery
10. What Is Stereotactic Radiosurgery?
    https://www.mskcc.org/cancer-care/diagnosis-treatment/cancer-treatments/radiation-therapy/what-stereotactic-radiosurgery
11. Stereotactic Radiosurgery
    https://www.aans.org/en/Patients/Neurosurgical-Conditions-and-Treatments/Stereotactic-Radiosurgery#
12. Gamma Knife Surgery
    https://my.clevelandclinic.org/health/treatments/16559-gamma-knife-surgery
13. Brain stereotactic radiosurgery
    https://www.mayoclinic.org/tests-procedures/brain-stereotactic-radiosurgery/about/pac-20384679#
14. Linear Accelerator
    https://www.radiologyinfo.org/en/info/linac
15. Stereotactic Radiosurgery
    https://www.aans.org/en/Patients/Neurosurgical-Conditions-and-Treatments/Stereotactic-Radiosurgery#
16. Stereotactic Radiosurgery
    https://www.hopkinsmedicine.org/health/treatment-tests-and-therapies/stereotactic-radiosurgery
17. Use of stereotactic radiosurgery in the treatment of gynecologic malignancies: A review
    https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4072821/
18. Ibid.
19. Ibid.
20. Stereotactic Radiosurgery (SRS) and Stereotactic Body Radiotherapy (SBRT)
    https://www.radiologyinfo.org/en/info/stereotactic#
21. What Is Stereotactic Radiosurgery?
    https://www.mskcc.org/cancer-care/diagnosis-treatment/cancer-treatments/radiation-therapy/what-stereotactic-radiosurgery
22. Advantages of stereotactic radiosurgery (SRS) over other radiotherapy techniques
    https://ui.adsabs.harvard.edu/abs/2005SPIE.5686..291B/abstract
23. Ibid.
24. Ibid.
25. Ibid.
26. Stereotactic radiosurgery
    https://www.mayoclinic.org/tests-procedures/stereotactic-radiosurgery/about/pac-20384526
27. Stereotactic Radiosurgery
    https://www.aans.org/en/Patients/Neurosurgical-Conditions-and-Treatments/Stereotactic-Radiosurgery
28. Ibid.
29. Immediate side effects of stereotactic radiotherapy and radiosurgery
    https://pubmed.ncbi.nlm.nih.gov/10030253/
30. Ibid.
31. Ibid.
32. Complications of Stereotactic Radiosurgery in Patients With Brain Metastases
    https://journals.lww.com/neurosurgery-quarterly/Abstract/2007/06000/Complications_of_Stereotactic_Radiosurgery_in.2.aspx
33. Stereotactic Radiosurgery
    https://www.aans.org/en/Patients/Neurosurgical-Conditions-and-Treatments/Stereotactic-Radiosurgery
34. Ibid.
35. Ibid.
36. Ibid.
37. Ibid.
38. Ibid.
39. Stereotactic Radiation (SBRT / Radiosurgery / SRS)
    https://www.oncolink.org/cancer-treatment/radiation/types-of-radiation-therapy/stereotactic-radiation-sbrt-radiosurgery-srs
40. Stereotactic Radiosurgery
    https://www.aans.org/en/Patients/Neurosurgical-Conditions-and-Treatments/Stereotactic-Radiosurgery
41. Stereotactic Radiosurgery
    https://www.hopkinsmedicine.org/health/treatment-tests-and-therapies/stereotactic-radiosurgery
42. Stereotactic radiosurgery
    https://www.mayoclinic.org/tests-procedures/stereotactic-radiosurgery/about/pac-20384526
43. Stereotactic radiotherapy
    https://www.cancerresearchuk.org/about-cancer/brain-tumours/treatment/radiotherapy/stereotactic-radiotherapy
44. Ibid.
45. Stereotactic Radiosurgery
    https://www.hopkinsmedicine.org/health/treatment-tests-and-therapies/stereotactic-radiosurgery
46. Ibid.
47. Stereotactic radiotherapy
    https://www.cancerresearchuk.org/about-cancer/brain-tumours/treatment/radiotherapy/stereotactic-radiotherapy
48. Stereotactic Radiosurgery
    https://www.hopkinsmedicine.org/health/treatment-tests-and-therapies/stereotactic-radiosurgery
49. Ibid.
50. Stereotactic radiotherapy
    https://www.cancerresearchuk.org/about-cancer/brain-tumours/treatment/radiotherapy/stereotactic-radiotherapy
51. Stereotactic Radiosurgery
    https://www.hopkinsmedicine.org/health/treatment-tests-and-therapies/stereotactic-radiosurgery
52. Stereotactic Radiation (SBRT / Radiosurgery / SRS
    https://www.oncolink.org/cancer-treatment/radiation/types-of-radiation-therapy/stereotactic-radiation-sbrt-radiosurgery-srs
53. Ibid.
54. Ibid.
55. Stereotactic radiosurgery
    https://www.mayoclinic.org/tests-procedures/stereotactic-radiosurgery/about/pac-20384526
56. Stereotactic Radiosurgery
    https://www.uclahealth.org/neurosurgery/dbs/stereotactic-radiosurgery#
57. Ibid.
58. Stereotactic radiosurgery
    https://www.mayoclinic.org/tests-procedures/stereotactic-radiosurgery/about/pac-20384526
59. Stereotactic Radiosurgery
    https://www.aans.org/en/Patients/Neurosurgical-Conditions-and-Treatments/Stereotactic-Radiosurgery#
60. Stereotactic radiosurgery
    https://www.mayoclinic.org/tests-procedures/stereotactic-radiosurgery/about/pac-2038452
61. Ibid.
62. Stereotactic Radiosurgery and Stereotactic Radiotherapy for Malignant Skull Base Tumors
    https://www.cureus.com/articles/29365-stereotactic-radiosurgery-and-stereotactic-radiotherapy-for-malignant-skull-base-tumors
63. Ibid.
64. Stereotactic radiosurgery
    https://www.mayoclinic.org/tests-procedures/stereotactic-radiosurgery/about/pac-20384526
65. Ibid.
66. Long-term Outcomes after Salvage Stereotactic Radiosurgery (SRS) following In-Field Failure of Initial SRS for Brain Metastases
    https://www.frontiersin.org/articles/10.3389/fonc.2017.00279/full
67. Ibid.
68. Ibid.
69. Stereotactic Radiosurgery
    https://www.mayoclinic.org/tests-procedures/stereotactic-radiosurgery/about/pac-20384526
70. Ibid.
71. Ibid.