Stereotactic Radiation Therapy (SRT)

Overview

Stereotactic radiation therapy is a specialized type of external beam radiation. It’s designed to deliver very strong doses of radiation to specific, well-defined areas. This precision is achieved through detailed imaging, clever computer planning, and very careful patient setup, ensuring the radiation hits its target with extreme accuracy. This concentrated approach means fewer treatments are often needed, making stereotactic therapy a convenient option for many patients.

What Is Stereotactic Radiation Therapy?

Stereotactic radiation therapy involves using multiple narrow beams of high-dose radiation that precisely converge on a tumor or abnormality. This technique allows doctors to deliver a powerful punch of radiation directly to the problematic area. The goal of stereotactic therapy is to maximize the damage to the target while minimizing exposure to surrounding healthy tissues and organs. This precision is particularly beneficial for small, clearly defined tumors that can be accurately visualized with imaging tests like CT or MRI scans.

Types of Stereotactic Radiation

There are two main types of stereotactic radiation, distinguished by where in the body they are used. Both leverage the core principles of stereotactic therapy: extreme accuracy and high-dose delivery in a limited number of sessions.

• 1. Stereotactic radiosurgery (SRS)

Stereotactic radiosurgery (SRS) is a specific type of stereotactic therapy that focuses on the brain or spine. Despite its name, SRS doesn’t involve actual surgery with an incision; no tissue is cut or removed. Instead, it delivers a very high dose of radiation in just one to five treatment sessions. This powerful, focused stereotactic therapy is often used for conditions like brain tumors (both primary and those that have spread from other parts of the body), as well as certain non-cancerous conditions affecting the brain or spinal cord. A team involving a radiation oncologist and often a neurosurgeon works together to plan and deliver this precise stereotactic therapy.

• 2. Stereotactic body radiation therapy (SBRT)

Stereotactic body radiation therapy (SBRT), sometimes called stereotactic ablative radiotherapy (SABR), is the application of stereotactic therapy to tumors located outside of the brain and spine, such as in the lungs, liver, or other areas of the body. Like SRS, SBRT delivers a highly concentrated dose of radiation in a limited number of treatments, typically one to five sessions. This form of stereotactic therapy is particularly useful for small, isolated tumors that might be difficult to remove surgically or treat with conventional radiation. The aim of SBRT is to provide a strong, targeted attack on the tumor while sparing nearby healthy organs from significant radiation exposure, a hallmark of all stereotactic therapy.

How Are These Treatment Systems Similar?

Both types of stereotactic therapy (SRS and SBRT) share key characteristics that make them highly effective and precise. These approaches are at the forefront of radiation treatment because of their ability to pinpoint and treat abnormalities with remarkable accuracy. The core principles of stereotactic therapy are consistently applied in both SRS and SBRT.

• They use multiple, narrow radiation beams that converge on the target.
• They precisely target small, well-defined areas.
• They rely on advanced immobilization devices or techniques to limit patient movement, or systems that monitor and adjust for movement during treatment.
• They deliver high doses of radiation safely and accurately over just a few treatments, usually one to five sessions.

How Do These Treatment Systems Differ?

While the underlying principles of stereotactic therapy are consistent, the application and specific capabilities can vary between different systems and techniques. These differences often relate to the location of the tumor and how precisely the patient can be positioned and monitored.

• Different capabilities: Some stereotactic systems are designed to treat only tumors in the head, while others can treat the head and neck, or even anywhere in the body.
• Different schedules: Some stereotactic treatments may be most effective when given in a single session, while others are better administered in a few treatments over several days.
• Different ways to achieve accuracy: Different systems employ various methods to keep patients in the correct position. Some use customized holders to keep the patient immobile, while others feature machines that track and adjust for any patient movement.

Risks and Side Effects of Stereotactic Radiation

While stereotactic therapy is designed to be highly precise and minimize damage to healthy tissues, like any medical treatment, it can have potential risks and side effects. These generally depend on the treated area and the individual patient’s health. The intensity and nature of side effects are often less severe than traditional radiation therapies due to the focused nature of stereotactic therapy.

• Fatigue: Feeling tired is a common side effect of many cancer treatments, including stereotactic therapy.
• Skin irritation: Redness, dryness, or sensitivity in the treated area can occur.
• Swelling: Temporary swelling around the treated area, especially in the brain, might happen.
• Nausea or headaches: These can occur, particularly with brain treatments.
• Hair loss: If the treatment area includes the scalp, temporary hair loss may occur.
• Specific side effects related to the treated body part:  The side effects often relate directly to the area being treated. For example, treatment to the lung area might cause a temporary cough, while treatment near the stomach could cause short-term digestive upset. Your doctor will discuss the specific side effects you might experience.

Stereotactic Radiation Results

The goal of stereotactic therapy is to effectively control or eliminate the treated tumor or abnormality. Due to the high, concentrated dose of radiation delivered with extreme precision, stereotactic therapy often leads to excellent results, especially for small, well-defined targets. Patients often experience a good quality of life during and after treatment due to the limited number of sessions and the reduced impact on surrounding healthy tissues. Your radiation oncologist will discuss the expected outcomes and monitor your progress closely after undergoing stereotactic therapy.