RADIATION THERAPY
How is radiation therapy performed?
Radiation therapy can be administered externally (EBRT – an external machine directs high-energy beams) or internally (radioactive sources are placed inside the body) always after examination and assessment by a radiation oncologist.
External beam radiation therapy (EBRT)
External beam radiation therapy (EBRT) is commonly used for lung cancer treatment.
Typically, a linear accelerator, often referred to as a “linac,” is the primary radiation machine used in this treatment.
EBRT procedure
Before starting EBRT, a planning session called simulation, is conducted. During simulation, measurements are taken to plan the radiation therapy. A body mold may be used to keep the patient still during treatment. Small dots are placed on the skin to guide the radiation beams.
Treatment begins a few days to weeks after simulation once a customized treatment plan is created and approved. All necessary safety and quality control checks are performed and calculations are confirmed by special equipment provided by all radiation therapy departments.
During each treatment session, radiation beams are aimed at the marked area without touching the patient’s body. The sessions are painless and typically brief, lasting 5-30 minutes, primarily focused on ensuring correct body positioning.
The term gy (gray) is now used to describe the dose of radiotherapy.
Gy is the new international unit of measurement of radiation dose expressed as absorbed energy per unit of tissue mass.
The radiotherapy plan usually includes a specific number of treatments given over a fixed period of time and varies depending on the stage of lung cancer, the type of radiotherapy and its objective. Indicative treatment plan for stage II or III lung cancer: 5 sessions per week (Monday-Friday) for 6 to 7 weeks, with a target of 30 to 35 treatments in total.
In addition to the weekly radiation therapy sessions, a weekly meeting is scheduled with the radiation oncologist to discuss and evaluate any side effects from the treatment. The meeting is held even when patients feel well. This discussion will determine the adjustment of the treatment plan always according to the radiation oncologist’s assessment.
Once the radiation therapy cycle is completed, patients are still monitored as often as necessary.
EBRT Techniques
EBRT includes various techniques, depending on what’s most suitable for patients. This is determined by radiation oncologists.
These techniques include:
Three-dimensional conformal radiation therapy (3D-CRT)
This method employs advanced imaging technologies like CT, MRI, PET, or PET-CT to create detailed 3D images of the tumor and surrounding area. By doing so, it enables precise targeting of radiation to the tumor while minimizing damage to nearby healthy tissue. 3D-CRT is particularly beneficial for irregularly shaped tumors or those near vital organs or tissues. All techniques are also combined with image-guided radiation therapy (IGRT), which allows the radiation oncologist to check the position of the tumor daily, at the linear accelerator, before treatment is given.
Intensity-modulated radiation therapy (IMRT) and Volumetric Modulated Arc Therapy (VMAT)
IMRT and VMAT also utilize three-dimensional imaging. They involve programming a machine to deliver highly focused radiation beams from multiple angles, precisely shaping the radiation dose to the tumor while minimizing exposure to healthy tissue. IMRT and VMAT are particularly valuable when treating tumors are located close to critical structures such as the spine.
Stereotactic body radiation therapy (SBRT)
Also referred to as stereotactic ablative radiotherapy (SABR), integrates image-guided radiation therapy (IGRT) with advanced techniques to precisely administer high doses of radiation to the tumor while minimizing exposure to surrounding healthy tissue. Unlike conventional radiation therapy, which spans several weeks with daily small doses, SBRT can be completed in just two to five sessions. When delivered in a single session, it is termed stereotactic radiosurgery (SRS). In the treatment of early-stage non-small cell lung cancer (NSCLC), particularly when surgery isn’t feasible or desired, SBRT is commonly employed, especially for tumors smaller than 5 cm or in cases with limited metastases.
Proton therapy
Proton therapy uses proton beams instead of X-ray beams for cancer treatment. Similar to X-rays, proton beams damage cancer cells’ DNA, causing their destruction. Imaging is used to precisely target the radiation. Proton therapy’s primary advantage is that all the radiation is released, reaching the tumor and falling off very sharply immediately afterwards.
Therefore, the damage to the healthy tissues in the area is limited, so we can deliver a higher dose of radiation to tumors.
3D-CRT | IMRT-VMAT | SBRT | Proton Therapy | |
When is it used? | Stage II-IV | Stage II-IV | Stage I or IV | Stage I-IV |
Main difference | Easiest type of radiation to deliver; less technical expertise required | Dose of radiation is shaped more conformally around tumor compared with 3D-CRT | Very high doses in a few fractions with sharp dose gradients; leads to higher rates of local control of the cancer | Reduces volume of tissue receiving low doses |
Internal radiation therapy (Βrachytherapy)
Internal radiation therapy, also known as brachytherapy, is another form of radiation treatment. It’s typically reserved for lung cancer cases where a concentrated dose of radiation in a small area is required, such as within the airway. During brachytherapy, a small radioactive source, often in the form of pellets or seeds, is inserted directly into or adjacent to the cancerous area, either through a bronchoscopy or surgery. This localized approach minimizes radiation exposure to surrounding healthy tissue. Depending on the type of brachytherapy, the radioactive material may be removed after a short period, ranging from several minutes for high-dose-rate brachytherapy to a few days for low-dose-rate brachytherapy. Alternatively, radioactive seeds may remain in place permanently, gradually decreasing in radioactivity over time.
