Stereotactic Body Radiation Therapy, or SBRT, is an advanced radiation treatment for certain types of lung cancer. It is a noninvasive procedure that delivers high doses of radiation with precision to a tumor. This technique targets cancer cells directly while minimizing exposure to surrounding healthy tissue. The goal is to damage the cancer cells so they cannot reproduce, allowing the body to naturally eliminate them.
The SBRT Treatment Approach
The principle of SBRT is the delivery of high-potency doses of radiation to a tumor in a condensed treatment schedule. This approach contrasts with conventional radiation therapy, which administers lower doses of radiation over many weeks. The precision of SBRT is comparable to using a magnifying glass to focus sunlight onto a single point, concentrating energy on the target.
This high level of accuracy is achieved through sophisticated technologies that account for tumor motion during breathing. Machines such as the CyberKnife or TrueBeam are examples of the linear accelerators used to deliver SBRT. These systems use advanced imaging and robotics to align the radiation beams with the tumor before and during treatment. This process ensures the high dose is confined to the tumor, which can lead to higher rates of tumor control.
Candidate Selection for SBRT
Determining who is a suitable candidate for SBRT involves a careful evaluation by an oncology team. The primary candidates are patients with early-stage non-small cell lung cancer (NSCLC) with small to medium-sized tumors that have not spread to lymph nodes. Tumor size is a factor, with ideal tumors being well-defined and five centimeters or less in diameter. The location of the tumor is also considered, as those situated away from central airways are more straightforward to treat.
SBRT is frequently recommended for individuals considered medically inoperable, meaning they have other health conditions that make surgery too risky. This can include elderly patients or those with significant cardiac or lung comorbidities. A patient’s performance status, lung function, and overall frailty are assessed to determine their ability to tolerate treatment. The decision to proceed is made after a comprehensive review of the patient’s cancer stage, tumor characteristics, and health profile.
The Treatment Journey Step-by-Step
The SBRT process begins with a consultation with a radiation oncologist to discuss the diagnosis and therapy. The next stage is a planning session known as a simulation. During this appointment, the medical team uses a 4-dimensional CT scan to map the tumor’s location and its movement during the patient’s breathing cycle. A custom immobilization device, like a body mold, is also created to ensure the patient remains in the same position for each treatment.
Following the simulation, the radiation oncology team develops a detailed treatment plan. This plan outlines how the radiation beams will be directed to converge on the tumor from multiple angles. This delivers a concentrated dose while sparing healthy tissue. The treatment sessions themselves are non-invasive and painless.
Most of the time during each appointment is dedicated to accurately positioning the patient on the treatment table using the immobilization device. Before each session begins, imaging scans are taken to verify the tumor’s position and make any necessary micro-adjustments. The radiation therapists then leave the room and begin the treatment, monitoring the patient from a control area.
The machine will move around the patient but will not touch them, and while it may make noise, the radiation itself is not felt. The entire course of SBRT is completed in one to five sessions over one to two weeks.
Managing Side Effects and Recovery
Many patients who undergo SBRT for lung cancer experience minimal side effects, which are often short-term and manageable. The most commonly reported effect is fatigue, which improves after the treatment course is complete. Some individuals may develop a mild cough or notice skin irritation in the localized area that received radiation.
Delayed side effects can develop months or years after treatment. One such effect is radiation pneumonitis, an inflammation of the lung tissue that can cause shortness of breath and coughing. If a tumor is located near the chest wall, there is a small risk of developing a rib fracture over time. The medical team monitors for these potential long-term effects during follow-up appointments.
Evaluating Treatment Outcomes
After the SBRT treatment course is finished, its success is evaluated through follow-up imaging scans like CT or PET scans. These are performed at regular intervals to monitor the treated area. The main goal is to assess “local control,” which refers to the successful eradication of the targeted tumor. SBRT is highly effective at achieving local control, with some studies reporting rates as high as 85-95%.
The radiation works to destroy cancer cells over weeks or months following the final session. Follow-up imaging allows the oncology team to track the changes in the tumor and surrounding lung tissue to confirm the treatment was successful. These appointments are also an opportunity to monitor for long-term side effects and check for any new developments.