Stereotactic Body Radiation Therapy (SBRT) is a precise form of radiation treatment designed to target tumors. This non-invasive therapy delivers intense doses of radiation directly to cancerous growths while minimizing exposure to surrounding healthy tissues. It serves as an alternative or complement to surgery for various types of tumors. SBRT aims to maximize therapeutic effect on the tumor while reducing potential side effects.
Understanding the SBRT Process
SBRT involves a condensed treatment schedule compared to conventional radiation therapy. Patients typically undergo one to five treatment sessions, usually spread over one to two weeks. Each session is relatively short, often lasting 30 to 90 minutes.
A detailed planning phase is essential for precision. Advanced imaging techniques (CT, MRI, PET scans) accurately map the tumor’s location, size, and shape. These images guide a customized treatment plan, and patients are often fitted with immobilization devices to ensure stillness during each session.
The Biological Response to SBRT
SBRT delivers powerful radiation doses that damage tumor cell DNA. This DNA damage prevents cancer cells from reproducing and growing, leading to their death. This process is not instantaneous; it unfolds over time. Cancer cells do not die immediately upon irradiation but rather when they attempt to divide after treatment.
After radiation delivery, the body’s natural processes clear away damaged cells. White blood cells remove this debris, which can sometimes cause an inflammatory response. Visible tumor shrinkage or inactivation typically takes weeks to several months to appear. Malignant and metastatic tumors may shrink within a couple of months, while benign tumors might take 18 months to two years to shrink. In some cases, tumors may not visibly shrink but instead become inactive and stop growing, which is still considered a successful outcome.
Monitoring Treatment Progress
After completing SBRT, medical professionals monitor the patient’s response to assess effectiveness. Initial follow-up typically occurs within four to six weeks post-treatment to check for acute side effects. Regular follow-up imaging is a cornerstone of monitoring.
Imaging tests (CT, MRI, or PET scans) are performed weeks or months after treatment to observe tumor changes. For instance, CT imaging for lung cancer patients is often recommended every three to six months for the first two years, then annually thereafter. These scans help doctors determine if the tumor has shrunk, remained stable, or if there are signs of recurrence. If recurrence is suspected but not confirmed by other scans, a PET-CT scan might be used. Alongside imaging, doctors monitor patients for symptom changes and overall well-being.
Factors Affecting Individual Response
The timeline for SBRT’s full effect varies considerably among individuals. Several factors contribute to these differences. Cancer type plays a role, as some cancer cells respond more quickly to radiation damage.
Tumor characteristics, including size and location, also influence the outcome. SBRT is generally most effective for smaller, well-defined tumors. The patient’s overall health and other medical conditions can affect their body’s ability to respond to treatment and recover. Whether SBRT treats a primary tumor or a metastatic lesion also leads to variations in observed response.